I've attached an Atwood wiring diagram and diagnostic aid. If no power is getting to the control board, you may have to look for the junction box on the front inside corner of the water heater. To gain access, you'll probably have to take down the rear wall of the pass through basement storage.
Also, before going to far, make sure your 12V DC supply is good. Nothing on the water heater will work without a good 12V DC supply. You can check the voltage at the battery monitor (with the holding tank monitor). On shore power you should have 4 lights. Disconnected from shore power, you should have at least 3 lights.