Does your battery have a full charge? The control board for the fridge and water heater generally operate from 12 volts and require a good battery to function properly. This is usually irrelevant of being plugged into shore power or not, though some will work from the converter, depending on the type of converter you have. I would check the battery first before doing a lot of other troubleshooting. An easy test would be to just unplug from shore power (assuming you are plugged in) and see if you have 12 volt lights etc. working properly. Good luck. More advice will follow I am sure.