To force-restart your iPad:
- On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
- On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.
A simple shut-down can be achieved by pressing-and-holding the Top button until the shut-down slider appears on screen - or directly from iPad Settings:
Settings > General > Shut Down