Scraping the sensor contact points to ground them worked.
It ended up being one of the side sensors. The driver side was screwed in with just one small screw. I bolted it in with two bolts thru the holes that did not have the backside nut preattached (unlike the right side and front). When I got done the sensor is slightly sloped backwards as the holes do allow the sensor to sit flat. It doesn't look like a new fender so maybe it came from the factory like that (who knows).
Any issues with the sensor not laying horizontal?
Thanks for all your help way2old.
Steve