Nexus 5x is not working, dim screen

Hello,

I've dropped my Nexus 5x after which it stopped working. However, when I press the power button I can hear the lock sound and the screen changes its color from grey to black (as if the phone would be locked) and vice versa. At the same time, I cannot recieve any notifications or phone calls.

I disassembled the phone and tried to reconnect all the flexes, but it didn't give any results.

Does anyone know what could cause this problem?