Is there a cylinder knob on a paintball 20oz tank?
Ah, I was not aware you were using a paintball CO2 cylinder.
Most paintball cylinders just have a pin that is depressed to release the gas. If you disconnect the regulator from the paintball cylinder, the gas will not escape due to this pin.
In any case, removing the regulator from the paintball cylinder and then allowing it to release the gas that is in the regulator is the fastest way to reset everything.