No Trailer Reverse Lights
 

I was cleaning up some wires on my camper and truck, and now I don't have any reverse lights. The reverse lights on the truck still work, but it's not making it to the 7 way trailer connector. I put a jumper wire on the camper and the reverse lights work on it just fine.
I checked the center pin in reverse and it's only getting about 2 volts. I'm sure I popped a fuse or something but I can't find it. I've checked every fuse in both fuse boxes and they are good. Is there a relay or fuse somewhere else that I haven't found?
I'm hoping to head out in a couple days and would really like to get this resolved.

It's a 1999 Silverado 3500. Thanks for your help.