Problem with new tail lights on boat trailer.

[Darkday]

I just redid the tail lights on my boat trailer because my old ones weren't working and the wiring was really old (trailer is 20 years old). The problem is the new ones don't work either. I suspect its in my grounding I have them grounded the the aluminium trailer. Do any of you know where else I could ground them ? Also I have a 7 pin hookup on my tundra but just have a 4 way flat on the trailer so I got a adapter when I look at the pins on the 7 pin side it has a little N like as in North. The thing is theres a little groove it has to fit into and then N is on the south side of the conector on my truck. seems odd but I guess it has to be right since there is a groove right ? Any help is appreciated