TM P226 re-assembly issue

[gorilla]

Hi, I bought a P226 that required a new valve knocker. I bought the part and fitted it. I have re-assembled the action as per the videos on YouTube. Now when the trigger is squeezed, the hammer does not fall. If you push the hammer dear with a screwdriver, the hammer falls nice and crisp as it should do. The de-cocker also works. Any ideas what I’ve done wrong?