You would have to know if the inverter is wired to any of the branch circuits in your RV. I would connect a known good 120v device (lamp, drill, etc) into the inverter's receptacle to see that it is functioning, first. If there are no wires connected to the inverter besides the 12v supply cables, your inverter is not wired to anything else. If there are wires from the inverter, in addition to the 12v cables, normally, they would go to a transfer switch and then to your load center. If your inverter has an internal transfer switch, the wiring from the inverter will route directly to the load center. If you can trace any wires from the inverter to the circuit breakers on the load center, you will find which branch circuits are powered by the inverter. Your GFCI's in the cabin will not test or reset without being powered.
