Help Phone will not turn on-Solid green LED

[PoptartWizard]

I plugged in my phone, HTC One M9, and left it overnight. I wake up in the morning (about 4 or 5 hours later) and it's fully charged, but the screen wouldn't turn on. I could double tap, and it made the vibration, but it only did it once. I have since unplugged it, and it's been off the charger for at least 6 hours. The LED is solid green, the display is still totally blank, and I don't get any feedback when I do anything with it.

I've browsed other threads and other forums, but no identical scenarios.

Any thoughts/ideas?

 

[Hadron]

Try pressing and holding the power key for 10-20 seconds until it restarts.

I've asked for the thread to be moved to the One M9 forum in case someone who owns the device has more ideas.

 

[SolApathy]

If your M9 doesn't respond when you touch the screen or press the buttons, you can press and hold the POWER and VOLUME UP buttons for at least 10 seconds. You phone will do a hard reset.