Stange Screen Colors after LCD Replacement

Hi,

I have made a LCD replacement with the guide. But when I turn on the phone, I see strange colors on the screen (check attached image).

I have even tried with different working LCDs, checked if connections were well seated,.. same problem.

Can you tell me what could be the problem?

And by the way, if there's something I could test or change?

Thank you very much.