Changed screen successfully multiple times but iPhone doesn't work.

I have a iPhone 4 running iOS 5. Lately I ordered a screen replacement for my iPhone 4 since the old screen’s logic board connector broke. I got the screen and it was in mint condition but after I installed it. I have order quite a few screens and none of them worked. I checked the logic board and the connections and everything is in perfect order. I also checked the battery, dock connector and all of the screens. They work perfectly as well.

I don’t know what is stopping the screens from working.