Replacement Screen stopped working after applying display protector

Hello,

my dad dropped his Pixel 4a 5G and the screen completely broke. We replaced the screen ourselves and this worked for a while.

When his display protectors arrived, i shut the phone off and glued them to the screen as described. However when attempting the restart it, it did not show anything anymore and it even seems that it didn't turn on at all (since there are no vibrations). When plugging it into a charger (even though the battery was full prior to this) it started to react to touch, it would vibrate whenever i clicked on where the pin numbers are, however the screen was still black.

I plugged the old screen back into the device and it also did not start (while the old screen is broken, the bottom half of it worked to a degree and it never showed anything there despite my attempts).

What can i do here/how do i diagnose the issue?

Thanks in advance!