iPhone 5s not turning on. *ANSWER*

So i bought a iPhone 5s from ebay for cheap. Seller said it didn’t work. Drawing 0 amps nothing at all. So I opened it up and replaced the battery, screen, dock connector but still nothing. So i decided to remove the shield protecting the A7 chip to see if there was any corrosion on it. Nope no corrosion. Decided to put the phone back together and… it turned on after removing the shield that came from the factory! I have no clue why this worked. Maybe it shorted out???? Just putting it out there so if anyone else has this issue they could try this! Thanks.