Cant power on with a non-original screen replacement!

Hi everyone!

I cant think of any other place to ask this, and if anyone has ever had this issue before please help.

So here it is. My client broke the screen of his 4s. I bought a non original screen replacement from ebay. When I installed it the device didnt want to boot up, i pluged it into the wall charger, my PC, no result - like its dead... So i decided to give it a try with some of my other screens, original (cracked but functional) and nonoriginal, not surprisingly it powered on... My guess was that the replacement was damaged, so i went to a local(!) store and bought a new screen, the guy at the shop showed me that it worked by connecting it to a 4s motherboard. When i came back and installed it, i was astonished by the fact that the new scree had exactly the same problem! Well alright..., its just a coincidence..., so i went back and explained the situation, barely convincing the guy at the store that it wasn't my fault. Finally, when i got the screen, i immediately installed it and what do think happened? Same story! Cant power on, no signs of live, nothing, just the processor heating...

Is the third screen! It cant be a coincidence! It just drives me insane! Idk what to do! I cant be that dumb to ruin 3 screens while successfully testing it with 4 other screens!

Please help me! It just doesnt make any sense...:((