three month i was changing pcb after pcb on the same unit like yours and finally it worked when i changed all of them except indoor pcb.
On your picture i noticed the same gray wires :the correct voltage is each wire to N is supposed to give 240V( in my case only one was live)
As for the main pcb - yes the red led is supposed to be off

You have to take a DC voltage at the red and black wires entering ACPower module.
If you have only a few volts 7-8 then the inverter is gone....
Take readings after the active power module incase it is working....