Are the wires attached properly in the plug?

Pull the plug out of the receptacle and if it is a Hubble brand or similar, not molded on, you can disassemble it and check the connections.

Start at the plug and work your way to the inverters.

Some have had trouble at the inside end of the shore cord where it is connected to the bus.

If you have a spare cord, plug it into the bus in the bay. That would proof out your shore cord.

JIM