They used to work sometimes and then sometimes wouldnt but now they dont work at all, im thinking it may be the switch. Can anyone tell me the easiest way to get to the switch and how to test it or any thoughts on what else it could be? Thanks

 

Bulbs check out ok? I would start by checking voltage at the plug for reverse light itself, then follow to the harness for the trailer lights, beyond that the reverse switch is in the range sensor for the transmission.