Don't make the assumption that the batteries are good. You need to disconnect the RV from power and read the voltage at the batteries with a multi-meter. 12V or less and the batteries are dead. If plugging the coach in now shows the batteries are charged, the batteries need to be replaced.
If you have no power and the batteries are still showing good then you should be able to use your multi-meter to follow the 12V power cable until you find a place where 12V power is no longer available. You should find a switch or a fuse (or a bad connection) at this location.