Seems the inverter, part # WR55X10855 is NLA, no longer available.
One of my suppliers has it subbing to WR55X10490
in lay mans terms WHAT!!
It make perfect sense to me
In short, check for 4-6 VDC from the main board to the inverter. No voltage means bad main board. Then check for 80-240VAC from the inverter to the compressor. No voltage means bad inverter. Then all that's left is the compressor.