iPhone 5S screen has black border and doesn't respond to touch

Hello,

I have a problem after replacing an iPhone 5S screen. The replacement screen touch functionality does not seem to work AND there's a black border at the top of the screen:

When I put the original screen back, the screen senses touch perfectly but the black border remains. Problem is I didn't test the phone before replacing the screen so I don't know if the black border was there before.

Here's a video showing the problem:

Also: the white strips are still white, so I don't suspect it has water damage.

Has someone experienced this before?

Sam