have you got the angel air turned off when your trying to fill it?
also what may be at fault is the flash tank assembly above the mini reg. the bolt holding it on could have come undone and causing air to leak out.
unscrew the mini reg and tighten the allen screw up that is inside the flash tank.
urrrm i thought it didnt matter if you had it off when you filled? ,
n i think ive sorted out the leaking from the volumiser just need some air to test.