[RMcNeal]

We have a 2019 3791RD. The large red key disconnect in the convenience center DOES NOT disconnect power from the battery to the level up system. Even with the key out (disconnected), the level up hydraulic system still works. Our residential fridge has a separate disconnect on the back wall behind the battery box. This is a round twist type switch with green and red indicators. This feeds power from the battery(ies) directly to the inverter for the fridge. There are a few other items such as propane and CO detectors that run off battery even when the disconnect in convenience center is disconnected. Confusing, I know.
That being said, even if your disconnect (red key in convenience center) was disconnected and pulled out, your level up system should be powered from your battery.
I haven't tried it, but I think the converter does not charge the battery bank when the disconnect in convenience center is disconnected. I basically never bother with that red key, it stays in and turned on. I have a separate knife style disconnect on my battery bank negative post to disconnect the batteries when in storage.
It could be that your battery hasn't been charging while in storage if the red key were disconnected.
As stated, your converter is behind the fuse box. If any of your 12 volt systems work while on shore power, such as lights, with dead battery or battery removed, then your converter is working.
If your fridge didn't work during power outage, check the inverter. Mine is mounted to the ceiling in the pass through basement on the ODS side. You should see a cord with a standard 110 Volt plug plugged into it. In addition the dedicated disconnect in the battery compartment, it has its own on/off switch too. Even with shore power, it should flash numbers in red to indicate how much power is being supplied to the fridge. It could be just turned off. It also has a GFCI receptacle, so check to make sure it isn't tripped.