Sounds like you either have a winding out on the PMA feeding the inverter or blown fuses on the inverter input.
There are fuses inside the inverter they look like resistors but are marked F1, F2 etc.
You can check the input to the inverter very easily by disconnecting the P15 and P16 connectors on the side of the inverter, start the set, it will run at max speed so you might want to adjust the black knob on the side of the engine half way between start and stop.
With a multi meter measure AC voltage on all the windings of the PMA at P15 and P16.
If you have all balanced voltages there then you have blown fuses in the inverter.
I cant tell you what the voltages will be because that depends on the engine speed so as long as they are balanced then you should be good.
You probably wont be able to get the inverter repaired by TRC so we may be in deep do do.