BUGGER … not good. Just for a long shot let’s try a reset.
Turn off power (ie remove power completely then re-power the power adapter but do not turn on the piano)
Press down the right-most white key (C7) and hold it down whilst pushing the power button. You will see the REC and PLAY LED’s flash for a short while - once the flashing completes release the C7 key.
Does it work now?
If not my best educated guess would be either bad RAM or corrupted ROM neither of which is repairable - needs new DM board.