or even a Desktop, the first suggestion I will make is that you retrace ALL your steps.
Go through the whole procedure again and this time make absolutely sure that you have not left some little lead or connector dangling in the breeze.
No video after the user has had the machine apart is a common occurrence
Once in a while I have to clear the dust in the fan of my MSI GP72-2QE 056NL. To access the fan I need to remove the heatsink, and to remove the heatsink, I have to unplug the EDP screen cable from the motherboard. After I cleaned the dust, applied some new thermal paste and plugged in the cable, I started my laptop. I hear the fan running and the power LED is on but the screen remains completely black. Even no backlight. In attempt to fix the problem I unplugged the power cable, removed the battery and held the power button for 60 seconds. After that the screen still didn't work. You guys have an idea what could be wrong? My best guess is the EDP cable, but I'm not sure. Anyone maybe have something I can try to resolve it? Otherwise I'll bring it to the repair shop.