i think what has happened is the bonnet (bit on the top of the tank regulator with the threads on) has unscrewed slightly (very common with guns without an on/off asa such as the invert mini)
if this is the case then it simply needs re tightening onto the regulator, this can be done by screwing it into your gun and continuing to screw the bottle in untill it tightens up again, then tighten both the small set screws
on the side of the bonnet to lock it in place
BUT!!!
do not do anything untill you have pics up as it could be a different problem and could be serious