After a screen replacement a strange issue happened.

Hello All,

I recently purchased a used iPhone 6 from a friend (who got it new). The iPhone's screen was destroyed, but in working condition (it was an OEM screen, I.E. it was the factory screen). I bought a replacement screen from a seller on Ebay. I replaced the screen, the good part of it was the speaker phone started working, but the bad was that the proximity sensor stopped working, which was no big deal for me. The screen worked fine for about 6 months, but today the cheap glue split the glass from the LCD. Once it split the internal parts such as the proximity sensor and the camera bracket came out. I opened the phone (after I shut it down) and took out the screws, then preceded to disconnect the flex cables. I put the internal parts back in place and they went in fine. I re-connected the flex cables and turned on the phone to check the LCD and digitizer to be sure it worked. The phone started up, but the screen only showed some backlighting, but no picture. The screen worked before I did this, but now that happened. Also when the phone fully turned on I got the notification sound (it was from Facebook). I turned the phone off and the proceed to check for the 'long screw' problem. The bottoms of the holes didn't appear to be scratched/depressed. I also did not put any of those screws back in after I took the screen apart, so it shouldn't be that. I ordered a new screen to replace it with. Any suggestions to help? Should I remove the battery connector for a few minutes and try again?

Thanks for any help you provide!

Thanks,

-John