Yep, if all the air is being dumped, but the bolt isn't moving, then I would suspect that the solenoid back check ball isn't sealing, or that the vent hole behind the can o-rings is too large.
The back check ball should be clean and round, and not have any damage - dents, nicks etc.
The optimum size for the ball is between 4.00mm and 4.10mm. A little larger is fine, but smaller isn't good.
The vent on the can should be just a tiny pin hole - 0.3mm wide.