WHen you disassemble, If you used the sear deactivation lever, you should have to push in the firing pin safety in order to move the striker forward. Once you have, you will be able to repeatedly move it forward, and will have to pull it back like it would be to catch on the sear in order for the firing pin safety to reset, and you may have to press the FPS to get proper unrestricted movement to do so.
If you take down by pulling the trigger, you will likely not have to press the firing pin safety as the striker moved into the forward position when tripped. I have had the sear just push the whole slide back enough that the timing was off and it hung on the FPS though, but not usually.