I've just updated my Google Nexus 5 to Marshmallow 6 and now the screen isn't responding.

[AC Question]

I can't answer calls, unlock it, nothing is responding.
Yes I have tried turning it off and on again....had to keep holding the on/off button down for an extended period of time to do this, couldn't just touch power off.
What do I do? How can I fix this?

 

[B. Diddy]

Welcome to Android Central! Was the update over-the-air, or did you manually install? When you held the Power button down, did it completely shut down? And when you tried to power back on, did it go through the whole boot procedure?