There's a device that lets the road engine charge the house battery. The house battery starts he genny and he genny can recharge it.
Just guessin' there's a bad connection, positive or negative, at the house battery. This is probably an ONAN, 4KW, series KY? Also has a logic board that could have one batty.
A coach I was looking at had a genny problem. I described it to a generator tech and he didn't think it was serious to not buy the coach over. There should be a price concession though.
If God's Your Co-Pilot Move Over, jd
2003 Jayco Escapade 31A on 2002 Ford E450 V10 4R100 218" WB