I just replaced my tail lights on my 88T2. I had problems with the brake lights not working on the right side. I made shure the harness was all good. No brake light on the rear tail lamp. All the lights come on when the parking lamps are on. But no go on the rear brake. And the stop light comes on the dash as well.

 

it could be that little button under the dash on the brake pedal, sometimes those will go bad and not open up, may want to check that.

 

If its only one side, I'd look at the ground wire for the lights on that side