Paul, if you haven't done it yet check the house voltage. An Elegant Lady should have 24 volts which if you are plugged into shore power or running the engine or generator should be reading at least 26 volts. Make sure the inverters and battery chargers are on. Our 97 is enough different than your 2000 so I am not sure you have the same inverter panels. Make sure in your 120V panel the two inverter and two battery charger switches are on.

The reason the voltage came up when you ran the engine is because the alternator was charging the house batteries and not the shore power so some switches, possibly the ones I described are off. If they are not off, verify you have AC power coming into the coach by operating something that is AC current that does not go through the inverter circuits.

It is critical you get those house batteries charged up.

Post your progress. I'll monitor this forum tonight till bedtime.