brake lights

I bought a Curt harness for my 2008 Rav and installed according to directions (even the durn battery wire that runs the length of the car!) and so far have only a hitch brake light with which to test it. I would eventually like to use it with a trailer, but I'm having trouble with the wrong...

Hoping for guidance on how next to troubleshoot this brake light problem. A driver behind me at an intersection jumped out to tell me that I had zero brake lights working. Not good! When I got home, I had someone mash the brakes while I watched. Both tail lights worked. There was no passenger...