Touch not working after screen replacement

Hi, thanks for reading. I have a friend's iphone 5s that has had a screen replacement. The new screen works alright apart from the fact that the touch doesn't work. There are occasions when swiping a finger on the screen would actually make a change and a menu might open but it doesn't generally respond.

I would be grateful if anyone can guide me on whether I will need to get a new screen assembly or could this be about a badly connected clip or something.

I have disassembled the phone only to the extent of separating the screen from the motherboard. I reckon the person who originally messed it up would have had to disassemble the components connected to the original screen as well so could going over those again help solve this? Or is the screen damaged beyond repair?

Thanks once again, I'll look forward to guidence.

Cheers