Do you have a hand held voltmeter ?
You need to get to both sets of batteries and test the voltages.
Do you have more than one disconnect switch?
Did you re-connect the batteries using the disconnect before you tried using the auxiliary start button ? Did you hold the auxiliary start button on while trying to start the engine ? Did you try starting the gen set while holding the aux start button?
You say you started the coach three weeks ago; when was the last time the coach was driven for several hours on the highway?