HTC One M8 Problem

[Proccoon]

My HTC One M8's screen is off but it's actually on and when someone texts or calls me the screen turns blue. I can't do anything with it. I held down the volume buttons and the power button for 2 minutes and nothing happened. It is also charging right now. Does anyone know how to fix this?

 

[Saga Lout]

To take the device back to factory settings and start again you need to press the volume + button and the power button, not both the volume buttons.