Ctslacker

Hey all new to the truck and forum . I'm having a problem with my snowmobile trailer all the lights work on the outside but my interior lights and the loading lights don't come on. I tried looking up on forums to see if I had to connect the wire in the engine compartment or mess with the back of the 7 pin plug . Can anyone help . Don't want to pay a dealer $$$ for something simple I can do. Any info will help Thanks