I use the Air Clamp, and I love it. I get about 1/3 inch expansion (above normal EG). I am gaining, and I attribute it mostly to my blend of pumping and clamping in the same workouts. The jelq sets are really just a warmup in my opinion.
I would email Monty about the problems you are having with the air clamp. Maybe you got a bad one? Before using it, make sure you have squeezed/flattened all the air out of it so it is real flat. Tighten the valve securely. Get as big of an erection as you can, carefully put it on as tight into your body/fat pad area as you can, and kegel hard and squeeze that bulb. You should get a great expansion.
Another thought, is your girth very large or very small, compared with the averages? I could see that possibly being a problem with those under 4.5” girth maybe. Another good question for Monty. I’m about 5” girth now, but I was only 4.6” EG when I started using the Air Clamp. Hope this helps…