Need help!!

Hey guys, I’m in a bit of a pickle here. I’ve recently inherited a 2021 Mercedes sprinter van built out by sync vans. I truly know nothing about how to maintain one of these but I’m doing my best to educate myself.

My recent problem is that both of the auxiliary batteries, that should be charging off of the alternator are dead. There’s a goal set and a blue battery whose name is escaping me. My question for yall is does anyone know of a shop, or somewhere I can go to have my van looked at near Missoula, MT? I’ve got a 5 hour drive today and I would love to get this fixed. I would just call sync vans but they went out of business. Thanks!