This was it, thanks! Nothing seemed to be able to format my card to FAT32 on Windows, however, so I used gparted on Linux to do it. After that, the update finished in a couple of seconds.

I'm enjoying the M1s so far, but for whatever reason, I can't install the 1.053 firmware update. I put update.dat into the card's root directory, then try updating the system. However, it always fails with "tf mount error".   Here is what I've tried: - Resetting to factory default settings -...