Everyone Check your Female 7 pin connector.....

I tow a TT, but this is related...

After a few years of towing I was having to really "jiggle" my trailer plug to get everything to work. I had to replace the bracket holding the truck's receiver plug so I just got a new bracket and plug.

Now everything works! If you are having to "play" with your plugs a lot to get them to work after a few years, it may be easier just to replace the plug(s).

Oh, and any work done by a dealer? Check and double check it!