Try a new pedestal. Unlikely the transfer switch will be in the battery area. It will have 3 50A wires, one from the shore power, one from the gen and one out to the rigs CB panel.
OK, 50A doesn't work, 30A with adapter doesn't work and gen doesn't work - correct? I would suspect the EMS or wiring to it. Could also be the ATS.
Find all of the 50A wiring connection points. Unplug the shore cord, gen off, solar off if equipped and Magnum inverter off. Remove panels and check all wiring for bad or loose connections. This includes all junction boxes and power cord connectors. Now is also the time to tighten all connections as they do tend to become loose.
If this doesn't help then get someone to start checking voltages for you.