I once connected the device to my computer. I tried to copy some files to it but it dissapeared from my list of mounted devices.
I thought I would try to repair the file system with the command fsck.vfat (I use a Linux computer), but it seemed to make everything worse.
Now I can’t play anything I copy into the device, it’s always “File format not supported”.
I tried to upgrade the firmware copying an upgrade.hex file into the root directory, but the upgrade failed. I formatted and restored to factory settings, but nothing seems to work.