Check the circuit breakers on the generator. One could be tripped. Reset the breaker by turning it off then on again. Do this with the A/C turned off so you don't cause arcing of the switch points.
You might also search online for a manual for your thermostat. It could need resetting, usually by pulling the fuse that protects the thermostat circuit or by turning off the house battery disconnect switch, usually near the entrance.
Is your RV a 50 amp or 30 amp unit? (50 amp shore cord has 4 prongs, 30 amp only 3)
If a 50 amp RV, check that both 50 amp breakers in the breaker panel are on.