Ok. so the valve that you're turning to adjust the amount of air allowed to enter into the jet has ABSOLUTELY nothing to do with the issue. Most likely the problem is some type of blockage in the actual jet, preventing the venturi action for drawing in any air. You should be able to fix this, from inside the tub. If you look in the center of the jet, there should be a piece you can unscrew. Once unscrewed, turn on the pump briefly and any debris should come out. There then though is the question of what and where this debris is/came from. Quite possibly it's the bypass valve in your gas heater that disintegrated.