Ok,
Distracted for a while but the good news is it is now fixed and working well.
Just not sure exactly what caused it.
I took the boards MPU and Driver to Skybeau (Ken's) again today and he replaced all the components in the circuit controlling that solenoid.
He tested before and tested after and on both occasions the boards tested fine.
When I plugged the board in, all works great. When I pressed the credit button, the solenoid energized and I could not believe it.
Ken can elaborate on what specific components he changed.
Most importantly, I really appreciated the support and help I received on this forum to sort out this difficult problem. People went above and beyond and that enabled me to get a solution. I look forward to the opportunity to help someone else on the forum when the opportunity presents itself!
In particular, Gavin, Boots and Ken, thanks heaps!
J.D.