X5 (E70) tow hitch wire harness installation

I am havging trouble with my wire for trailer.
I just installed my tow hitch today and also completed wire set up.
However, brake light on the trailer (4 pin connector) does not come up when you put the brake pedal.
it is working fine with turn signal and night light. BUT What happen to the brake light? Anybody has any idea? Please, let me know.
for installation, it took me about 7 hours. If anybody needs advice for installation, i think i can help you little bit.

But i need to solve the problem with brake lights first.

Please, let me know if anyone has any idea. I already checked all the wire and eveything was in right place.

Id like to know what your tips are. I am going to be doing this install in about a month.

Also, have you had the dealer reflash your car? That might fix the brake lights.

D

What happened here???

Are the brake lights L.E.D. ? If so they may not work.