4 pin break light not engaging

[Bohen]

So planning my road trip to California go to pick up a trailer from ufailure from u-haul hook it up and the brake lights are not engaging on the trailer we check multiple trailers as well as different harnesses.
I called the dealership and they said the TSB for the recall is not my vehicle's Vin number and does not affect it so with that out of the way trying to rack my brain around it tomorrow I'm going to be checking for loose connections and maybe soccer and maybe sacrifice a chicken or 2.
The fuse is fine right and left light work work perfectly it is just when I engage the brake for the trailer.

Does anybody got an idea on what it may be I know it's not working most likely lose connection but all input and advice welcome .

Thank you

 

[Erock75]

Same issue here, Did you figure it out?
Thanks

 

[2020Telly]

Check for an improper ground. The other option could be a higher amperage draw than the harness can handle. If you try LED bulbs on the trailer this might drop it low enough.