I have seen this before when Replacing screens on other notebooks and there have been a couple reasons one of the big ones is when the plug for the screen is reinserted if you are not using anti-static band it will short out something on the motherboard. I replaced a screen for a student on a Chromebook and was not using my anti-static band . I did however have the battery disconnected and it still happened. I sent it into dell for warranty work and that was what they said caused it to fail Luckily we do enough business with them they fixed it anyway. Other things I have seen is the cable being crimped and causing the cable to fail. Hope this helps. Good luck