Why won't my printer print this queue item? Using the queue inspector

A queue item is sitting there, a printer is free, and nothing happens. Almost always this means the item and the printer don't match on something - the wrong filament, the wrong color, the wrong nozzle, the wrong bed, or a rule that's keeping them apart. SimplyPrint can tell you exactly which one. This guide is the complete reference: it shows you how to open the printer-compatibility view (the queue inspector), and then walks through every single reason an item and a printer might not match, what each check looks at, and how to fix it.

This is the most common queue question we get, so it's worth understanding how matching works once. If you're new to the queue, start with the print queue overview and come back here when something won't start.

In this article

• How printer matching works
• How strict is matching? The criteria settings
• Open the queue inspector
• Worked examples: what matches and what doesn't
• Material type mismatch (PLA vs PETG)
• Color mismatch (the big one)
• Nozzle size, type, or volume
• Bed type / build plate
• Custom tags
• Print size doesn't fit the build volume
• Temperatures the printer or filament can't reach
• Not enough filament left
• Missing or invalid slice (analysis)
• The printer can't run this file type
• The item is assigned to specific printers, models, or groups
• The queue group excludes the printer
• It's a virtual group item
• Not a compatibility issue: the printer is out of the matching pool
• Not a compatibility issue: the item is paused or on the back burner
• Let the to-do list do the work
• Related articles

How printer matching works

Before a printer can start a queue item, the two have to agree on every requirement at once. The item carries a set of needs - a material type, a color, maybe a nozzle size or bed type, a size that has to fit, temperatures, custom tags, the file type its firmware can run, and any printer/model/group restrictions you set on it. The printer has its own configuration - what's loaded, what nozzle and bed it has, what firmware it runs, and which groups it belongs to. A match happens only when the printer satisfies all of the item's requirements. Miss one, and the printer is skipped.

That's why a free printer can sit idle next to a full queue: it isn't "broken", it just doesn't match any of the items right now. The inspector turns that invisible decision into a plain-English list of which printers can run the item and, for the ones that can't, exactly why not - using the same labels you'll see in the rest of this article (Material, Color, Nozzle size, Bed type, Tags, Size, Temps, Filament, and so on).

How strict is matching? The criteria settings

Not every check below is enforced, and you decide which ones are. Your account has a queue matching criteria setting (in Settings › Print queue) and a separate AutoPrint matching criteria setting (in Settings › AutoPrint) that turn individual checks on or off. If AutoPrint criteria aren't configured, it falls back to your queue criteria. You can also click Adjust matching criteria inside the inspector to toggle a check and instantly see printers re-classify before you commit anything.

Here's every check and its default:

Choosing a strictness level - the workflow:

• Leave the defaults unless a specific mismatch is blocking work you know is fine. The defaults are deliberately in the middle: precise enough to protect your prints, loose enough that printers don't sit idle over trivia.
• Tighten for production to a spec - turn colors up to Exact match, keep Strict material type on, and switch on Nozzle type/volume if those matter. A wrong shade or nozzle then becomes a non-match rather than a bad print.
• Loosen for prototypes, jigs and internal parts where you just want the queue to use whatever's loaded - drop colors to "Any color", or turn off Strict material type so any PLA counts.
• Prefer clusters over disabling a check. If "Textured PEI" and "Smooth PEI" are interchangeable for you, group them in a bed-type cluster rather than turning bed matching off - that keeps the check working for everything else. Same for colors (color clusters) and materials (material clusters).

So if you're surprised a printer matched (or didn't), check your criteria first - the rule you expect might simply be turned on or off.

Open the queue inspector

You can reach the same printer-compatibility view from two directions.

From a queue item (the "why won't this item print?" direction):

1. Open the item's big item view (click the item in the queue).
2. Find the Printer compatibility card.
3. You'll see which printers can run this item, and for each printer that can't, the reason it was excluded.
4. For the whole picture, use the link at the bottom of that card to open the full queue inspector - a per-printer breakdown of every printer and why each one can or can't run the item.

From a printer (the "why is this printer idle?" direction): open the printer's control panel and use its print-queue widget to inspect the other way around - which queue items this printer is able to run, and why the rest are excluded. Both views read the exact same matching rules, so they always agree; use whichever direction matches the question you're asking.

The rest of this article walks through every reason a free printer might not start an item: first the compatibility reasons the inspector reports, then the queue-status and matching-pool cases it deliberately leaves out.

Worked examples: what matches and what doesn't

A few concrete scenarios (default settings), to build the intuition. In each case, the inspector names the exact reason.

Notice that most stuck items fail on exactly one thing. The inspector tells you which, so you change one thing and move on.

Material type mismatch (PLA vs PETG)

Inspector label: Material. The item is tagged for one material family (say PLA) and the printer has something else loaded (say PETG), or nothing recognised. A printer won't run PETG parts in PLA just because it's free, because the two slice and print completely differently.

Two things worth knowing:

• By default, matching uses the specific (branded) material type - so Generic PLA won't match Bambu Lab PLA Basic. If you turn off Strict material type match in your matching criteria, matching drops to the family level, so any PLA matches any PLA.
• If you deliberately treat two materials as interchangeable (for example a house-brand PLA and PLA+), you can group them with material clusters so they match each other.

What to change:

• Load the right material into the printer, or update what SimplyPrint thinks is loaded (assign the correct spool), or
• If the item's material tag is wrong, edit it on the item, or
• Set up a material cluster if the two really are equivalent.

Color mismatch (the big one)

Inspector label: Color. This is the single most common reason items don't match, and it's the one people misunderstand most, so it has its own full guide: why won't my filament color match a printer? In short, SimplyPrint matches on the actual color - both the color name and the hex code - not just the name. So a printer can be excluded because the color name is different, or because the hex is different, even when the two colors look similar to you.

The two ways to fix a color mismatch are color clusters (group colors as equivalent) and color mapping (replace one color with another), both reached from the Color matching modal. The dedicated article walks through exactly when to use each. If your items aren't even getting the right color tag automatically, see auto-tagging and auto printer-model selection.

Nozzle size, type, or volume

The item can require a specific nozzle, and there are three separate checks:

• Nozzle size (label: Nozzle size) - for example 0.4mm vs 0.6mm. This is an exact match and it's enforced by default, because nozzle size changes the sliced result.
• Nozzle type (label: Nozzle type) - for example hardened steel vs brass. Off by default; turn it on in your matching criteria if it matters for your workflow.
• Nozzle volume (label: Nozzle volume) - for example a high-flow nozzle. Also off by default.

What to change:

• Swap the printer to the nozzle the item needs and update the nozzle on the printer in SimplyPrint, or
• Correct the item's nozzle tag if it's wrong, or
• If you don't actually care about nozzle type/volume, leave those checks off (they already are by default).

Bed type / build plate

Inspector label: Bed type. The item is tagged for a specific build plate (for example a textured PEI plate) and the printer has a different plate fitted. This matters when a print's adhesion or finish depends on the surface.

If you have plates that are interchangeable in practice, use bed type matching to group them: bed types in the same cluster are treated as equivalent, so when one matches, all others in the cluster are accepted too.

What to change:

• Fit the bed the item expects and set the matching bed on the printer, or
• Group the plates as equivalent with a bed-type cluster, or
• Relax the item's bed requirement if any plate will do.

Custom tags

Inspector label: Tags. Custom tags are free-form labels you create (for example "high precision" or "dialled in"). The rule is simple: the printer must carry all of the item's custom tags. A printer may have extra tags the item doesn't - that's fine - but if the item requires a tag the printer doesn't have, it's excluded.

What to change:

• Add the missing tag to the printer, or
• Remove the tag from the item if it isn't really required.

Print size doesn't fit the build volume

Inspector label: Size. The object is larger than the printer's build volume, so it physically can't print there. A job to print a large object won't be sent to a printer with a small bed. This check also covers nozzle count and extruder count - a multi-color print that needs more extruders or tool positions than the printer has is excluded here too (the inspector may show these as their own Nozzle count or Extruder count labels; printers with an AMS-style system that can map colors to a single extruder are handled automatically).

What to change:

• Send the item to a printer with a big enough build volume, or
• Scale the model down and re-slice if that's acceptable.

Temperatures the printer or filament can't reach

There are two temperature checks:

• Temps (label: Temps) - the file needs a bed, nozzle, or chamber temperature that exceeds the printer's hardware maximum (or needs a heated bed/chamber the printer doesn't have). The printer physically can't get there, so it's excluded.
• Filament temps (label: Filament temps) - the file's temperatures fall outside the range of the filament currently loaded on the printer, beyond an allowed margin. This protects you from, say, running a 260°C profile on a filament set up for 210°C.

What to change:

• Send the item to a printer that can reach the temperatures, or
• Load a filament whose temperature range fits the file, or
• If the file's temperatures are simply wrong, re-slice with the correct ones.

Not enough filament left

Inspector label: Filament. If the printer has tracked spools assigned, SimplyPrint checks whether there's enough material left to finish the job. A printer that's nearly out won't be handed a print it can't complete. This check only runs when you assign real spools (static material tags aren't tracked by weight).

What to change:

• Load a fuller spool, or update the remaining amount on the assigned spool, or
• Assign a spool with enough material to the printer.

Missing or invalid slice (analysis)

Inspector label: Analysis. Most of the checks above (size, temperatures, filament amount) rely on the file's G-code analysis - the read of what the sliced file actually does. If an item hasn't been sliced yet, or its analysis is missing or invalid, those checks can't run and the item won't auto-match.

What to change:

• Slice the item (or wait for slicing to finish), then it can be matched.

The printer can't run this file type

Inspector label: Unsupported file. Some printers can't run certain file types at all. For example, a Bambu Lab printer in cloud mode can't print raw .gcode meant for a different firmware, and some formats depend on a minimum firmware version. When the printer's firmware can't run the item's file, it's excluded, because sending it would just fail at the machine.

This is a hardware/firmware capability check on the printer - it is not the same as a queue group's accepted-file-types setting, which is an add/move-time membership rule (it controls what you can put into a group, not what the inspector reports). For that, see queue groups.

What to change:

• Send the item to a printer whose firmware supports the file, or
• Re-slice or re-add the item in a format the target printer can run.

The item is assigned to specific printers, models, or groups

Inspector labels: Not assigned, Model not assigned, Group not assigned. Every queue item can carry its own restrictions: allowed printers, allowed printer models, or allowed printer groups. If you (or an integration) pinned the item to specific printers or models, every other printer is excluded by design - even a perfectly capable one.

What to change:

• Open the item and check its allowed printers/models/groups.
• Widen the selection (or clear it) so the printer you want is included.
• If the restriction is intentional, this is working as designed - load up one of the printers it's actually allowed to run on.

The queue group excludes the printer

This is the one that trips people up most, so read it carefully. A queue group has a for printers / models / groups setting. That setting controls which printers the items in that group are allowed to MATCH and print on. If the group is set "for" a certain set of printers and your free printer isn't in that set, items in the group will never run on it.

What to change:

• Open the group editor and check its "for printers / models / groups" selection.
• Add the printer (or its model/group) to the group's allowed set, or
• Move the item into a group that's pointed at the printer you want to use.

This matching-not-moving behaviour is explained in full in queue groups. If items seem to "not move" to where you expect, that article is the one to read.

It's a virtual group item

Inspector label: Virtual group. If the item lives in a virtual queue group, it is never sent to a real printer by design. Virtual groups are for tracking work you're not actually starting through SimplyPrint (outsourced or off-platform jobs), so there's nothing to match - you advance these by hand with +1 finished and Mark finished.

What to change:

• Nothing, if you meant it to be virtual - mark progress manually.
• If it should print on a real printer, move the item out of the virtual group into a normal one. See queue groups.

Not a compatibility issue: the printer is out of the matching pool

Some printers won't take new work even though they'd be a perfect compatibility match. These printers are removed from the matching pool before compatibility is ever checked, so they don't show up in the inspector's reason list at all - you spot them from the printer's own status and from the queue counts, not from the inspector. Two cases do this:

• Maintenance or out of order. A printer marked as in maintenance or out of order is taken out of the matching pool on purpose, so the queue won't hand it new work. Automatic starting (1-Click Print and AutoPrint) skips these printers too. See printer maintenance for how maintenance status works.
• The bed isn't cleared. If you have printer beds must be cleared turned on (a 1-Click Print setting), a printer whose bed still holds the last print won't be offered a new item until the bed is marked clear. This is a safety setting so you don't start a print on top of a finished one. The queue page has an Awaiting bed clear count that jumps straight to the printers waiting on a clear.

What to change:

• Finish or cancel the maintenance, or take the printer out of its out-of-order state, and it rejoins the pool.
• Clear the bed physically, then mark it cleared in SimplyPrint, and the printer becomes eligible again.
• If you don't want the bed gate, you can turn off "printer beds must be cleared" in queue settings - but most farms keep it on for a reason.

Not a compatibility issue: the item is paused or on the back burner

These are queue-status states on the item, not compatibility problems, so the inspector ignores them - it inspects raw compatibility regardless of whether the item is currently eligible to start. A paused item stays in the queue but won't be picked up until you resume it. A back-burner item lives in a separate low-priority lane; depending on your settings, automatic matching may skip it. Items still awaiting approval, or from a user who is over quota, are also held back at this layer rather than by the inspector.

What to change:

• Resume a paused item to put it back in play.
• Move a back-burner item to the normal queue, or start it manually.
• Approve a pending item (if you're an approver), or sort out the user's quota. See scheduling and distribution for how automatic matching treats these.

Let the to-do list do the work

Reading the inspector item by item is great for one stuck job. When you want the whole farm sorted, use the to-do list. Every time you open it, SimplyPrint reads your entire queue and works out the single highest-impact physical change that would unlock the most prints right now - then hands it to you as a checklist.

So instead of opening ten items and discovering ten "wrong filament" reasons, the to-do list tells you "put PLA in this printer and it can print 16 items", grouped by queue group, with one-click actions to set the tag, assign a spool, or jump to the printer. It's the same matching logic the inspector uses, turned into a prioritised worklist. The two work together: the inspector answers "why won't THIS item print?", the to-do list answers "what should I physically change next to unblock the most prints?".

If a printer keeps ending up idle, it's also worth checking how the queue is set to distribute and order work - see scheduling and distribution. Settings like "never skip queue items" change whether a printer waits for the right filament or moves on to something it can print.

Related articles

• Why won't my filament color match a printer?
• All about the "Tags" feature
• Auto-matching queue items to printers
• The print queue: overview
• Queue groups
• The to-do list
• Scheduling and distribution
• Printer maintenance
• Auto-tagging and auto printer-model selection

Updated on: 04/07/2026