I have the MA version shield and Just installed the apex trigger spring and sear and sear spring and now it wont engage. I cycled the slide and pull the trigger and nothing happens the firing pin doesn't release or something is going on. Does it matter having the factory MA striker block and could be causing this?

Don't have a clue. Have you tried talking with APEX about it? If so let us know what you figure out. I'm happy with the trigger on mine but then again I wouldn't know any different as I'm pretty new to shooting.

Contact Apex. They'll walk you thru the install.

Same thing happened with my new .45c. I installed the entire FSS and trigger kit. When finished, it would not release the striker. I believe I have isolated the problem to the Apex trigger, because with that trigger installed the trigger bar doesn't retract rearward enough to fully engage the sear. When I put the M&P trigger back in (but leave all other Apex parts installed), the trigger bar does move rearward far enough to engage the sear, which in turn releases the striker and allows the pistol to fire. I sent a note along with photos and videos to Apex Tactical asking for their comments and advice.

Randy Lee (Apex Tactical) has a video on youtube on that very subject.

Sorry to say, but not a good idea to replace perfectly good parts. Ending up with a gun that will not work is worse than having a gun with a "compliant" trigger pull.