If your iPad is locked up, we recommend you perform a hard shut down on your iPad. To do this, hold down the Home and the power buttons simultaneously for 20-30 seconds.
If using an iPad Pro or an iPad without a Home button, follow the steps provided by Apple, found here: https://support.apple.com/guide/ipad/restart-ipad-ipad63d30b5a/14.0/ipados/14.0#iPad715e3eec
Note: Depending on the iPad you have, and the version of iPadOS installed, you may need to use a different method. For example, on an iPad Air 5th Generation, the volume up/down buttons are not in the same position as on the iPad Pro. You need to use these steps to perform the shut down:
1) Press and quickly release the volume button nearest to the top/power button.
2) Press and quickly release the volume button farthest from the top/power button.
3) Press and hold the top/power button for at least 12-30 continuous seconds.
4) When the Apple logo appears (usually after 12 seconds,) release the top/power button and the iPad should restart.
The above steps are found here: https://support.apple.com/en-ca/guide/ipad/ipad9955c007/ipados
For further assistance in how to force an iPad to shut down, please contact Apple support.