Replaced iPhone 6s+ screen has backlight but no image, original works.

I cracked my iPhone 6s+ screen and so bought a replacement from iFixit. When installed the phone turns on but the screen shows no image, backlight however is functional. Reseating the connectors + phone reset did not help but installing the old cracked screen immediately worked every time.

Thinking I got a dud screen I got iFixit to send me a replacement, but the new screen has the EXACT same issue. Phone turns on, backlight ok, no image. Old screen still works 100% fine. And yes the screen was installed with the battery connector removed.

At this point I have no idea what is going on as there is obviously no board damage and I can’t be installing the connectors wrong if every time I put the old screen back in it works, which I have done multiple times. I’m almost willing to just give up but if anyone has any ideas that’d be great.