[Carl n Susan]

With only one battery, the refer inverter will draw down the battery charge. I don't know if would be enough to prevent the Level Up system from working. If it were me I would go for second battery.

I see you have a Ford which comes with the fuse and relay for the 12V Charge line unlike a Chevy. Ensure the 12V charge line in your RV outlet is actually working. For some reason, the fuse protecting that circuit has a propensity to pop stopping the 12V to the trailer.