Looking for some advice on problem with our Mastervolt Mass Combi 2000/12-100.

Returned to the boat Friday eve after 7 weeks to find batteries completley dead, the shore power was  disconnected while away.
So plugged in shore power and left to charge the batteries without issues.
On sunday eve after returning from restaurant the mass combi was not outputting and all the LEDs where on on both the main unit and remote panel.
No amount of restarts, ditching power to both batteries and mains and restarting made any diffetence.

Sequence is:
Switch to on
Fan starts
Individual load and charge leds sequence
Mains power outputs breifly the combi shows all leds steady illuminated and unit stops outputting and fan stops but LEDs remain illuminated.

I have checked boat 240v wireing and combi 12v supply all are fine.
Also checked the combi thermal trip and external fuses.
I have confirmed there is 240v at AC in and 12v at the combi’s  battery terminals.

Any advice very much appreciated