Lights on a HF 4x8 Trailer problem

[The Ruckus]

I just assembled my HF 4x8 Trailer and added the lights matching color to color. Easy, or so I thought.
Connected the 4 pin to my Ford explorer with proper tow connector (color wires matching)

All lights work correctly until I hit the brakes.

They don't work, plus if I have the signal on, it goes off too.

Checked all the color matching connection and all are good.

Any Ideas?
I have a DMV appointment in 2 hrs...

[KCStudly]

Probably a grounding issue.

[The Ruckus]

After hours of messing around scratching paint to get grounds, I finally run a straight line from the rear lights to the neg on the battery. The lights worked. Missed my appointment though...

[Redneck Teepee]

After hours of messing around scratching paint to get grounds, I finally run a straight line from the rear lights to the neg on the battery. The lights worked. Missed my appointment though...

90% of all electrical problems are ground issues on trailers. Sounds like you discovered and solved it though, good luck at the DMV.