Trailer lights not working!?!?

I know this is a old thread but im trying to get my father in laws 2012 trailer lights to work . I used a volt meter on the trailer pins and im not getting power at the tail light pin. I checked the fuses under the hood all have 12v running through them. Where is this box exactly that’s supposed to be behind the driver seat. Father in law has a AC . I was thinking about jumping out the 12v pin to the tail light pin to give it 12v any info would be great

 

Well, at least in a 2003 Extended Cab model, the fuses are in a "access" (see what I did there?) panel behind the drivers seat on the shelf. See picture.

 

I have exhausted my Google-kung-fu on this one...
2013 Access Cab PreRunner with factory tow package.

I have no ground at the plug, but I do have power. I chased the plug pig-tail back one connection to check for ground continuity there and... nope. If anyone has seen this before please help.