OK, I'm back on this, thanks everyone who has contributed so far but unfortunately the problem still exists.

Id be putting a meter across the switch to make sure its operating first, then diagnose why the signal is not being read if need be

Retropin, I have tested the switch and I think it is OK but can you be more specific about how to test it and I'll make sure?

Try reseating connector 1J4 on cpu board (2nd connector fom left, along top of cpu board.)

Thanks Stevesee but no change