By any chance has it been stored in a hot garage for an extended period, top down? Mine was and evidently the top material shrunk, stopping the top about 2 inches short of the header. I gently pulled it manually both with the pump running and without, it still didn't come down all the way and I could see how tight the material was. Luckily, the top was kind of shot and I was just beginning work on the car, so replacing the top is already in the budget. I don't know how it might be re-stretched if this is the problem.
