Trailer reverse light won't work

The trailer reverse light on my Connector at the bumber is not working. All other connections work (turn signals, brakes, lights). I need this to work so that the disc brakes on my trailer deactivate when I am backing up. Any ideas on how to trace this? Thanks for your help
Toppump

Not sure but did you check and see if it had a seperate fuse. My running lights on the trailer stopped it it was a fuse.

Which connector type are you using for the trailer? Most are NOT wired for reverse lights.