You may hard reboot your camera to power it down, if it is not responding to usual shutdown commands.
This will not undo any saved settings on your camera. It will remember your logged in streaming accounts and any saved WiFi networks. This is not a factory reset. To revert your camera to a factory reset, please read this article for directions.
The best way to power down your Mevo camera is to press and hold the top button for three seconds.
If the camera does not respond to this, press and hold the top button for 30 seconds. Then power it back on. This will hard reboot your camera.