If Gary is talking to the buyer, he probably has covered these, but the Troubleshooting guide says:

The Fade In/Out button might be on, muting the sound.

Make sure the LOCAL CONTROL button is set to ON

All keyboard parts are set to OFF. Use PART ON button to set to ON

Master volume may be set to low.
(never know on this one. If he's using a volume pedal and did not turn the master up)