Flickering screen after replacement

There are a few reasons this could be happening but these are the main ones

1 - Bad connection for the lcd when you put it in (try unclipping and putting them back in)

2- You have pinched the ribbon cable putting it in ( with the screen plugged in and the screen on move it slowly back and forth in the air and see if the screen comes good)

3- You put the screws the hold the cover on the lcd/touch/sensors connectors in the wrong order and possible damaged the motherboard

4 - The lcd ribbon / lcd itself is bad.,