Weird trailer connector issue, lights not working?

[brm98]

Getting our travel trailer ready to head out for our first trip this year I decided to hook it up to the GX for the first time to text everything. Plug the harness in to the 8 pin connector and no lights, no signals, no brake lights. However, all the light come on on the trailer when the headlights are turned on???

I know the trailer is good since it's not even a year old and worked great when I towed with the Grand Cherokee just a few months ago.

I'm wondering if anyone on here has had a similar experience? What could be the cause?

 

[joabmc]

Did you test the connections? My trailer lights don’t come on until the GX lights are on as well but the brake and turn signals work.
There is a diagram on the inside of your cover. Find a ground the ground and you can easily test each operation.