The power issue is either a GFI outlet that has tripped or the inverter. These are the outlets with a red reset button on them. You may have only one or two on your coach.
The other thing to check is the circuit breakers on your inverter itself. Most usually have two circuit breaker buttons that can trip. These are on the inverter and NOT in your main circuit breaker power panel.
I should have added that your salesman switch, usually by the door, may have be switched off which would keep 12 volts from going to either the WH or the furnace. With no 12 volts, neither will work.
