OK, unless I'm retarded can someone tell me why I can't get the tail lights to work on my other trailer? I can get all lights to work on one trailer but another I can't seem to get the tail lights to work and when I do have the light switch on NONE of the lights work on this particular trailer. Simple four wire diagram....anyone have any ideas?

 

ground.......

 

Could be a bad ground. I'd also check the bulbs. I know that sounds dumb but can't hurt to check.