Help diagnosing parking sensor problem...

[sshu]

I got into an accident where a car hit the driver side door. I took it to the body shop and when they completed the car I now have a parking sensor issue. They had to remove the front bumper when doing the repair. The problem is,

-When I start the car the front left and rear right sensor beep once.(always happens)
-When I push the parking sensor button the light flashes.(sometimes happens)
-When I put the car in reverse the parking sensor light flashes.(sometiems happens)
-When I put it into drive or park the sensor beeps once.(always happens)

I suspect something may have been damaged when they pulled the bumper off. I cleaned the sensors and it didn't help. The body shop doesn't know how to fix it. They pulled the front bumper to check things and cleared any codes but it doesn't work. Does anybody have any exp with possible causes for this problem? Any help would be great so I can help the clueless body shop.

Thanks,