[MadMax]

Sounds like the pilot valve seal is toast. Most regulators bear a spring against a moving piston which either pushes on a needle valve stem (common to many paintball regs) which opens an inlet. This allows gas from the high pressure side to push into regulated side. Eventually gas pressure raises in the regulated side which changes the piston direction so it lets off of the valve. Adjusting the screw changes the setpoint by adjusting the spring force exerted to the piston. The piston's recharge setpoint is caused by the summation of the spring and atmospheric pressure balancing against the opposing regulated chamber pressure.

Anyways, long and short I suspect that the valve that controls gas flow between your bottle and regulated pressure chamber is broken. Either that, or your piston is jammed by broken oring bigs from your side tap plug so it's seized in the opening position.