6S Image display turning on and off during replacing screen

Okay so long story short, I’ve been practicing screen replacement & whatnot, and I’m having an issue that I haven’t had to deal with yet.

Iphone 6S, originally water damaged. The screen was stained and had dark spots, and the touch didn’t work in the centre.

When doing the screen replacement, I tested my new screen without unplugging battery (that’s what the dude did in the video I watched). The new screen worked perfectly; and then I unplugged the screen, then I remembered to uplug the battery.

I switched over my Touch ID home button, and my front camera/audio piece.

Then when I plugged it in, it worked, but as I went to put new adhesive on, it stopped working?

The back light was showing, but there was no display. Even if I shined a light, there was no display. But the phone still vibrated when I plugged it in, and it vibrates when I tried to “put in my password” on the blank screen. You could hear the buttons making the noise that they were pressed. So everything was working but my display. But as I was fooling around with it, the display would randomly start working.

I tested my old screen and it did the same thing, so I know it isn’t a screen issue

I thought it may have been a loose connector in the logic board, where the digitizer connects, so I disconnected the battery and screen, and used isopropyl alcohol & a tooth brush to remove the adhesive from the logic board.

Even after doing all of that, I still can’t find anything wrong.

I can’t see any loose, broken or bent pins. And after watching YouTube videos about backlight dudes, and LCD driver repair, I can’t see any similar issues in mine?

Thanks for any help you guys can give me!