Brutus,
It sounds as if your transfer switch (the switch box that switches from shore to generator power) is malfunctioning. They sometimes get stuck in one position or just plain fail. I would listen for a loud click after you have plugged in the coach shore power. Make sure your breaker is off before plugging in shore power, then plug the coach into the outlet, then flip the breaker on. You should hear a loud click or pop, if you don't your transfer switch isn't opening to the right position and may be stuck or bad. Either way replace it if you hear nothing when turning on the breaker. You may also have a battery charger from your shore power to your house batteries that is bad or unplugged. That would be your secondary thing to check. Where these boxes are varies widely from coach to coach. In our 07' Tourmaster they are under the bed in back.
I hope this helps
JB