Operator error - problem solved
Following up on my post from 12/30. House batteries were dead and couldn't get past the low voltage lockout despite having 15 amp shore power. Then we had a sunny and warm day (38+ degrees) and the solar panels were generating 50-75 watts. The combination of "warm" weather + slow charge reset the BMS and I'm back to normal.
On my long drive into cold weather, I did not have the battery heater on. I made the bad assumption that driving and running systems would keep the battery at an operating temperature and it would continue to charge from the alternator or shore power when we landed. Be extra dilligent in cold weather! If the sun hadn't come out to help us, I'd still have a frozen and dead house battery and therefore, no heat, no generator, no lights, etc.