Ok Motor homes have two batteries as a rule (or two battery banks)
Engine and House (Chassis and House, or Main and Aux)
They also have a converter and an isolator
IF you are plugged into verified 30 amnps (AC will work on FAN in cold weather on COOL in hot weather not not select COOL in cold weather)
Then check the following in order
IF YOU HAVE AN INVERTER. The inverter display panel.. THEN the circuit breaker feeding it
IF NOT The ciruit breaker feeding the CONVerter
The Converter
Make sure Batteries are CONNETED (Aux and main both)
Finally
The Isolator.. Some have Bi-Direcitonal (BIRD Bi-direcional Isolator Relay Delay/Device) some have one way isolators (ENgine charges house house does NOT charge engine)
To test that. USE digital volt meter. Measure battery voltages .. Take notes
Plug in, come back in 2 hours and measure
12.6 FULL resting
13.6 FULL Charging (Float)
Assorted volteages while charging.
IF you get 13.6 on house but 12.x on chassis. ADD Trick-L-Start.