So I have tried everything. Even bought all new brand new lights, wires, etc. I have the tail lights and turn signals working but the brake actually turns the lights off? What could be causing this? Thanks,

Your owners manual should tell you what is needed. Some cars can use a 4 pole, some need a 5. Depends on how the brakes are wired with the turn signals.

It sounds like you may have a poor ground. Don't assume the hitch has a good connections. Make certain the White wire has a clean secure ground on both the vehicle and the trailer.

I'd focus on the hitch and clean all connections, particularly grounds.

Thanks. I have tried running directly from the adapter, brand new harness, right to some brand new tail lights and ground to trailer frame and still same outcome. I took all other connections and wires out of the equation to troubleshoot. Crude diagram attached. I even plugged my other trailer in to see what would happen there and got the same thing? Seems like it might actually be an issue starting with the vehicle?48358