Welcome to iRV2.
Sorry your first post is about problems .
Three possibilities .
The auto transfer switch , is not passing power into the coach .
The circuit breaker in the main panel that powers the inverter is tripped or bad .
Internal controls in the inverter that automatically , switch the unit from invert to charge the batteries are defective.
Circuit breaker is easiest to check .
THEN if circuit breaker isn't the problem . Try the roof air conditioner .
The roof air , isn't on an inverted circuit , so if that works then , the auto transfer switch is probably ok.
Questions .
Is this a 30 amp RV or a 50amp ?
Do you have a volt meter , and are you confident in it's use ?