Open up the backbox and check ALL fuses. Take them out one at a time and verify their value (finely etched into the end cap) matches what is called for in the manual. Continuity beep-test them with a meter. All correct and good?
Refer to manual and locate and verify ALL status LEDs on Power Driver Board and WPC controller. Are any unlit?
Inspect around the three batteries on the WPC controller board for fuzzy white or green stuff.