[JRTJH]

It sounds like you may have a functional electrical connection "AT" the input to the main breaker and possibly a "DISCONNECT" at the output of the main breaker. I'd suggest you unplug your RV, take the faceplate off the electrical distribution panel, remove each circuit breaker and look to see if there are any issues with the connections at the bus bar. If those connections are good, then look carefully at the circuit breakers. It seems "impossible" that they could all fail at the same time, but a strong spike in the AC input could have burned them all. (think lightening strike, etc) The "switches" on the circuit breakers would still operate, but the "insides" wouldn't function.

If the breakers are all operational and functioning, then trace the circuits from the breaker connection through the Romex to each appliance. It could be as simple as a loose neutral (white wire) at or near the breaker box bus bar.

Good Luck