Suggestion...
Have the trans in Neutral and use a depth gauge to measure from outside of the case down thru the switch mount hole to the reverse shift rail...write down the measurement....
Now put the trans in reverse and check the depth measurement again...it should be greater....
If its the same measurement, sorry its bad news...you may have the shift shaft itself in 180 degrees out of phase, placing the reverse detent on wrong side of shaft to allow switch to operate....
The shaft will still operate,,,the detent ball and spring will compress enough for shaft to operate.
It doesnt happen very often, but I have seen it about five times over the years...
