What remote panel do you have?
It should show
* Battery voltage
* AC input status
* AC Breaker size
When on shore power with the charger enabled what is the battery voltage?
It should quickly jump to 14Vdc or so if not, check for AC input status and Charger enabled status.
If the panel says all is good with no error codes.
Suggest you remove the unit from the rig and do a bench test - many times the internal transfer switch craps out.
PLEASE do not toss it in the trash if you decide to purchase a new unit. As I collect them for spare parts and repairs as time allows
