Does it still fire okay? IF you dry-fire it, the trigger feels normal? I ask because there is a little ball bearing in the safety lock. If it got dislodged (I don't even know if it is possible), it could prevent the cam from turning (assuming it then moved to a spot it could jam the cam).
I hate to ask, but, you are turning it clockwise, right? It's odd, as this is a very simple device without much to go wrong.
Maybe, however, your slide is not in full battery. Your finger should be away from the trigger and you should be holding the pistol in such a way as to keep the slide & frame aligned properly. Maybe you are holding it in such a way that is causing the slide to be moved ever so slightly? Try verifying the slide is in perfect position. Then place the pistol on a counter top, and attempt to turn the lock. Hope that helps.