The file does not show up on the printer or is not recognised: format, folder and card

Symptom

The microSD card or USB drive is read, but the file you copied does not appear in the list on the screen, or it appears and the printer warns that it is not compatible with it.

Likely causes, from most to least likely

1. You copied the model, not the sliced file: the printer only prints the file the slicer exports for it (G-code or its brand's format), not the STL or the project. Bambu Lab asks you to export the plate sliced file.
2. Sliced for another printer or with another profile: Bambu Lab asks you to choose the right printer model and plate when slicing, and Prusa warns «The G-code isn't fully compatible» if it does not match the installed printer or nozzle.
3. The file is inside a folder: on the P1, Bambu Lab asks you to save it in the card's root, not in the folders already on it.
4. An incomplete copy or a card removed without ejecting: Bambu Lab warns that hot-plugging can damage the card or corrupt its contents.
5. A format or card the printer does not support: Elegoo asks for FAT32 with a 4096-byte allocation unit and under 32 GB on the Neptune 4, and Bambu Lab supports FAT32 up to 2 TB when formatted from the printer.

Checks to tell which one it is

• Check how you exported it: it must be the sliced file for your printer, not the STL or the slicer project.
• Check in the slicer which printer, nozzle and plate you chose when slicing.
• Check on the computer whether the file is in the root or inside a folder.
• Try the card or drive in the computer: if not even the computer reads it, it must be replaced (Elegoo).

Before you start

Before taking anything apart, cleaning or adjusting it, switch the printer off and unplug it, unless a step says otherwise, and do not touch the nozzle, the heater block or the bed until they have cooled down. If in any doubt about electricity, heat or moving parts, stop and ask a professional.

Step-by-step fix

1. Slice and export for your printer

   Open the model in the slicer, choose your actual printer, nozzle, plate and filament, slice and export the sliced file (in Bambu Studio, the «Export plate sliced file» option). Copy that file, not the STL or the project.

   Check: The new file appears in the printer's list.

   If that does not fix it: Check where you saved it (next step).

2. Save it in the root and eject properly

   Save the file in the root of the card or drive, not inside folders. Eject it before removing it from the computer; and on printers that require it, such as Bambu Lab's P1 and A1, also eject it from the screen (Settings, SD Card, Eject) before taking it out.

   Check: The file is complete and can be opened.

   If that does not fix it: If the printer says it is not compatible, check the profile (next step).

3. If it warns that it is not compatible

   When the printer says the file is not for it (on Prusa, «The G-code isn't fully compatible»), compare the printer model and nozzle in the slicer with the machine's (on Prusa, in Settings, Hardware) and re-slice with the right ones.

   Check: The printer opens the file without warnings.

   If that does not fix it: Check the card's format (next step).

4. A format and capacity your printer supports

   Back up what you want to keep first: formatting erases everything. Format to FAT32 on the printer itself if it can (Bambu Lab: Settings, SD Card, Format) or on the computer. Windows only offers exFAT from 32 GB up (Bambu Lab, Prusa); for the Neptune 4, Elegoo asks for under 32 GB in FAT32 with a 4096-byte allocation unit.

   Check: With the freshly formatted drive, the file appears.

   If that does not fix it: Try another card or drive (next step).

5. Try another drive and a test file

   Copy a test file from the maker (Elegoo provides one for the Neptune 4) to another properly formatted drive. If it appears, the previous drive is faulty; if not even the test file appears, the printer's port, cable or board may be failing (Elegoo, Creality): contact the maker's support.

   Check: You know whether the drive or the printer is at fault.

   If that does not fix it: Follow your maker's support instructions.

Prevention

• Always export the sliced file for your printer and save it in the root.
• Eject the card or drive before removing it, from both the computer and the printer.
• Use Class 10 or U1 cards or faster (Bambu Lab) and keep a spare.

Still not fixed?

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Printers it applies to

Any FDM (filament) 3D printer, from any brand.

Official sources

This guide summarises the official documentation linked here:

• How to print from SD card using Bambu Lab P1 Series 3D printer · Bambu Lab
• FAQ for Printing from micro SD Card · Bambu Lab
• The G-code isn't fully compatible (CORE One, MK4S, MK4, XL, MINI) · Prusa Research
• SD cards and USB drives · Prusa Research
• Neptune 4 Series: Unable to Read USB Drive · Elegoo
• Unable To Read USB Drive (K1 series) · Creality