I would place a mulitmeter across the battery bank and determine that the on-board Heart Freedom 20 interface inverter is supplying the three different DC charging voltages to the battery bank when on Shore Power or Generator.
If you do not see these DC Voltage increases on the battery terminal than measure back towards the DC output terminals of the Inverter/Charger unit and see where you are loosing the DC Voltages.
Could be as simple as BATTERY DISCONNECT switch engaged or blown fuse/breaker between the Inverter/Charger and the battery terminals or even bad connections at the battery bank...
When I read my fully charged battery bank I read around 12.6-7VDC across the battery terminals. When I connect to Shore Power or run my connected generator I see an increase to 13.6VDC or higher depending on the on-board Inverter/Charger charging mode at the battery terminals.
Roy Ken