The source of power to the inverter should be a 30amp breaker in your AC power panel. If your coach is 50amp service and you are plugged in to a 50amp outlet, there is the possibility that one leg of the circuit is broken. Check the outlet for 240VAC across the two legs. If OK, check that 240VAC is inside the AC power panel. If not check that both legs are getting through the transfer switch. If the power is getting into the transfer switch but one leg or both are not getting through the switch, the transfer switch is probably defective. If both legs are not getting to the Transfer switch, look for a problem in the main power cord or plug.