Why aren't the motion sensors on my leviton occupancy sensing switches working?

I'm currently a maintenance man and when i started here about six months ago the occupancy switches in the staff kitchen only worked when they were manually operated. We purchased 2 new occupancy sensors and I installed them, this time grounding them to their respective GEM boxes as the 2 switches prior were not grounded (not that it would effect their operation in theory anyway), and the new switches had the same problem. I adjusted every setting available and still they would only operate manually. So I we bought 2 more and I installed them and they won't detect motion either. If anybody can help it would be greatly appreciated.Why aren't the motion sensors on my leviton occupancy sensing switches working?do what every maintenance guy does, double check wiring, than replace the unit. and be aware, even though you are a professional, there is still such thing as an owners manual.

~if all else fails- there's always the clapper model.

~unless i am misunderstanding, you said "manually operated" are you saying you have a switch operating the proximity switch? blank out the box and have the wiring go directly to the prox sensor.