Why is the screen flickering and also has faint white lines.

I installed the new ifixit iPhone 8 replacement screen onto the phone and when I started the phone up and got into the home screen, the screen was very low resolution, the screen was flickering and there were some white bars that were going vertically across the screen. Before I installed the screen I also noticed that on the screen flex cable connector there was a darker smaller pin that was different from the rest of them. I want to ask the community for some tips in fixing this problem before I have to return the product. Some help would be appreciated.

Thanks,

Dominik

Jurcins