I have the exact same problem.
Firmware does not update, and Arturia button flashes when turning the unit on.
AFCC says update, and "performs update" says, "success"
next time I turn unit on, same thing.
Support have told me to delete software, reset pram, try different cables and ports, and try another computer to do update.
I have tried all to no success.
I have also tried a hardware reset of the unit (holding mono on startup)
all combinations bring the same result... upon restarting the unit, flashing power/arturia button and asking to update the firmware in the software.
Very frustrating,
Please help!