X2 Printer won't read 3rd party USB flash drive

I tried using two different USB drives to upload files to my X2. I get a message that there are no files on the drive. I am a Nubie and assumed I was doing something wrong. I then pulled out the USB drive that came with the printer. The printer read it with no problem. I then transfered the Filament Clip file from my 3rd party USB to the Artillery USB and it read it. So why won’t it read my flash drives? Is there a special formatting that Artillery uses? Any suggestions? Anyone else experience this? HELP!

I would recommend formatting to FAT32 which should work.