Try resetting the unit from the boot loader menu:

1) turn the unit off.
2) turn the unit on
3) after powering on, when the display shows “Waiting for scanner”, press the [Transpose] button.
4) this will bring you to what is called the Boot Loader Menu - on the screen you will see :

“Install FlashROM”
via MIDI

5) press NO (-) button once, you will see

"Hard RESET"

6) press Rhythm/Metronome button to invoke.
7) press YES (+) button to confirm

The unit will blink out as if it is turning off/on again at which point it should be completely factory reset.

If this fails to revive things, or if you cannot even enter this menu, then unit will need service.