Chosen Solution
Yesterday I did a self repair on my 2015 MacBook Pro retina, following the instructions here MacBook Pro 15" Retina Display Mid 2014 MagSafe DC-In Board Replacement When I reassembled everything and powered on, my MacBook screen remained black. I plugged into an external monitor, to confirm that everything but the display seems to be working. I double checked the display data cable, confirming that everything was connected, and that the pins weren’t damaged. Things looked good What else could be happening? Possibly relevant detail: The only slightly suspicious thing that happened when I was re assembling was that as I was putting the logic board in and aligning all the ports, there was a small click sound. I’m prettty sure it was the board/ports clicking into place, but I suppose there’s some chance it could have been something cracking.
Clearly something popped! Did you leave a screw under the logic board or put the wrong screw in as there is one place a short screw is needed. Review Step 30 in the guide you used.
