Check that the coach/house battery switch is "enabled" (coach batteries are "enabled"). Usually near/in the stepwell, near the side entry door.
If not, consult the Owner Manual if you have one, or go to the manufacturer's website and download.
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)