Before you do anything else put the pistol back together and grab a pencil. Jack the slide back to cock it and stick the pencil down the barrel point the pistol up and pull the trigger. The pencil should get launched if the firing pin is working.
If it doesn't then move on to these steps:
Does the plunger move in and out freely when you push it down with a small punch? Take it out and clean it if it doesn't.
Do you have an adjustable trigger stop? The trigger bar activates the plunger lever and if the trigger bar isn't going back far enough the lever wont push the plunger in far enough to clear the firing pin. If this is happening back off on the trigger stop screw a bit and test again with the pencil.
If none of this stuff works send it to me and I'll fix it for you.
