Yes, give the various restarts a shot (although the final 3-button might not work if Power button is non-responsive)
To fix an issue, try these in order:
Restart using the Battery Icon and press Restart
Press and hold the Power button for 10-15 seconds. Then leave it for 20-30 seconds and see if it restarts.
To REBOOT:
Press and HOLD all three keys for about 10 - 20 seconds: PowerOn, VolUp and VolDown. Start with the PowerButton. Keep holding past the 3-choice options screen. If you hear a shutter type sound, you've taken a Screen Shot and probably missed the PowerButton.