Use a small left-handed drill bit... it bites into the head and removes the screw.

Getting the ribbon cable pinched under the glass during installation might cut one of the conductors in the ribbon cable. Be sure to carefully route the ribbon cables during installation.

The cable connecting the speaker module to the logic board was not reconnected OR the screw connecting the cable to the case was not reinstalled. Note this is NOT an answer to the question about the non-working phone, which seems to have been liked.

Try putting the broken screen back in. If it lights up and works, you got a bad screen.