02 Tahoe Trailer Reverse Light

I have the standard factory trailer plug (round) on my 02 Tahoe that I’m not getting any juice out of the reverse light port, I checked the fuse they all seem to be fine, is there a switch I need to activate to get power to that port ?
When the trailer is plugged in everything works on the trailer except the backup light. we checked the bulbs (ok) and traced the wiring all the way to the plug with out any power.

Any Idea ?

If you have the factory trailer plug the centre pin should have a light green wire on it which is connected to a 10 amp fuse (trailer b/u lts) in the upper left corner of the fuse center under the hood. If the 25 amp b/u lp fuse is ok and the 10 amp fuse is ok you should have 12v at the centre pin when the transmission is in reverse. Hope this helps some.