I was in a similar situation last week and learned the difference between coach & chassis batteries, as configured on my coach. Basically, plugging in to shore power charges the coach batteries but not the chassis batteries. Because my chassis batteries were about five years old, ended up doing a full replacement. This after a bunch of troubleshooting, cleaning, servicing & ineffective charging.
I have a conditioner charger on the chassis batteries right now and ordered the famous Trik-L-Charge solution this morning
This does not directly answer your question, but gives you some issues to consider.
Cheers, Good Luck & Enjoy The Ride.
PS - start a maintenance log now to start documenting what went wrong and how it was resolved.
Bob & Patty Smith
both USAF Retired