As a last resort, if all the previous methods have failed, you can interrupt the power to your PC to cause it to totally shut down. Note that this is very much a last resort as it doesn’t allow your PC to complete a controlled close down and in rare cases can actually cause issues which then prevent Windows from starting properly.
Desktop PC only: If your PC is mains powered (ie. doesn’t contain a battery) you can simply switch off the power at the wall outlet, wait at least 30 seconds, switch the outlet back on and then use the PC power button in the normal way to switch back on.
Desktop & Laptop PC: Press and hold the power button for 10 seconds. Before trying it is important to note that the moment you press the power button the screen may go blank or show “Shutting Down” but you must continue to hold the power button or a full restart won’t be achieved. Once you’ve held the power button and the PC is off, press the button in the usual way to switch back on.