Batteries could be bad.
If you have a toad or a neighbor, use jumper cables to the 12 volt chassis battery to get it going. After 10-15 minutes try to start the genset. It should have enough charge. The charge relay under the hood should energize after chassis battery has some charge. It (charge relay) will if it is good charge the system.
If you have a meter, check the charge relay for voltage after main engine has run. The voltage on each side of the relay should be what the alternator is putting out.
If you push the "aux" start button on the dash you should hear a click from the charge relay. The charge relay and the aux start uses the same relay.
