When you remove the firing pin assy you're supposed to squeeze the cocker until the end of the firing pin is flush, and then turn 90 degrees clockwise. On my pistol it's not quite 90.
When you replace it, start at 3 o'clock until you get past the sawtooth, then wiggle it between 2 and 2:30. Once it's in as far as it will go, you'll push another eighth inch against spring pressure and rotate from 2 or 2:30 counterclockwise up to 12:00.
Do this with the slide on the frame.
Try it and report back.