Domestic Thermostat E7 code off 12V for heater

[muskypicker]

Dometic autocorrect to domestic. Nice. Long title but trying to specify what we're seeing.

2018 25' International. Had it for two years, never any HVAC issues. This morning we tried to run the heater and are getting an E7 code that means there's no 120Vac, which makes sense because we're not plugged in to shore power. AGM Batteries are at 90%. Everything else electronic seems to be working. Tried a thermostat reset and toggling the battery disconnect on and off. Still getting the error.

Any ideas? Anniversary trip is a little chilly right now...

Thanks a ton!
Chris