I just installed a new PSA FCG in my new GF3 receiver, and the disconnector won't engage with the hammer. Everything appears to be oriented correctly, at least compared to my WASR-10. Do I need to do some final fitting, or do I have a bad part?

ETA: It isn't just the disconnector. The trigger sear hooks don't catch the hammer when cycling the bolt carrier either. I can push the hammer down with my finger and the sear engages, but not when cycling the bolt carrier.

Update:

I removed the PSA FCG from my GF3 and the Tapco G2 from my WASR-10 and swapped both FCGs. Now I have to broken guns. The PSA FCG behaves the same in the WASR and the GF3. The hammer does not catch when cycling the bolt, and the disconnector doesn't hold onto the hammer with the trigger pulled.

The Tapco G2 FCG, a previously known good FCG, doesn't work in my GF3 now. Same symptoms. The one common element, besides potential operator error, is the pin retaining plate. I have not been able to reinstall the retaining hook in either receiver, so I've been using the same plate in both receivers.

This is really getting to be irritating. What am I doing wrong?