What happened?
The printer is showing the message "Use a different USB drive or reformat this one to the supported FAT32 file system".
Error name: USB drive unsupported file system.
Error code: #26703 (MK4S) #13703 (MK4) #27703 (MK3.9S) #21703 (MK3.9) #31703 (CORE One)
This error is shown when the USB drive is on the wrong format.
How to fix it?
Make sure that your USB drive is formatted to FAT32. Is the issue persists, try using another USB drive.