This really sounds like a bad NEW main board.
You would be surprised how many come in this way! Im a feild tech so I see this all the time its frustrating to say the least.
The wiring is almost never the problem. O I suspect you got another one with problems. Make sure also when you return that board, that you tell them to make sure that you have a PRE Programmed PROM.
It sounds like that may very well be the issue, either a non programmed IC or a bad main board.
Thats exactly what I woudl do, and I have been service appliances for over 30 years.
Best chance of quick success that way ;-)
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