Auto body repair & detailing: rear bumper sensors, minor fender bender, buick rendezous

Question
I had a minor fender bender with my 2006 Buick Rendezous.  The whole rear bumper assembly was replaced, etc.  Now my rear backup sensor system is not working.  The auto body place has to check w/their dealer supplier, but after thinking about it, they painted & clear coated the whole bumper including the sensors.  Could this be the cause of it not working?  They checked that all the overhead wires were connected, there's no reset as I can tell (this is what their checking with their supplier for).  The next thing is they'll have to pull off the bumper again.  The painting/clear coat seems like a simple answer, but I know nothing about autobody work.  Have you had anything happen like this?  Thanks for your input.

Answer
the sensors are meant to be painted- they actually come in a special little box from the factory that you paint a new sensor in. I doubt this is the cause - I believe there is wiring damage, or the new harness is faulty. I got a new faulty harness for a rendezvous about 5 months ago. I would start there. Bill