Top of touch screen won't respond to touch after screen replacement

I recently replaced the whole display of my iPhone 6S plus with the ifixit kit. I tested the touch functionality before sealing it up and everything seemed to be working fine. But as it turns out, the top 10% of my screen won’t respond to touch. So I can’t swipe down to get to notifications or use the Back Menu buttons in my applications.

I’m pretty sure I’ve got all of the connectors for the digitizer seated properly but I could be wrong. The rest of the screen works well and it’s just that top 10% that doesn’t respond.

Before opening it up again to check the connections, I wanted to see if there were any specific reasons why only the top of the screen wouldn’t be functioning. Hopefully that clue will give us a better idea where to start.