iPad stuck in guided access, won’t restart

It is a common misconception that an iPad (or iPhone) can remain fully functional with damaged or defective physical buttons. 

Whilst Accessibility features (such as assistive touch) can be used to augment the User Interface, these features cannot be used as a substitute for physical button sequences that must be used to trigger system recovery actions. Sooner or later, as perhaps now, you will encounter a situation from which you cannot recover.

If your iPad has a known issue with function of the Home or other physical button, your iPad will require repair:

iPad Service & Repair - Apple Support

Otherwise, you might be best advised to seek assistance directly from from Apple Support. You can contact the Support Team using the Get Support link at top-right of this page. Alternatively, if you have access to another Apple device, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:

https://apps.apple.com/gb/app/apple-support/id1130498044

You might also consider a visit to the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to asssit:

Genius Bar Reservation and Apple Support Options - Apple

When you are stuck in Guided Access mode, you are really stuck as the typical triple tap on the home button to quit out of Guided Access doesn't work. Even a forced exit won't work because the power button and the home button are disabled. 

The only way to get out of Guided Access is to press the Home and Power button together for 15 seconds. This should turn off Guided Access by forcibly rebooting your device. Once your device is restarted, you can then go to Settings > Accessibility > Guided Access > Guided Access - and turn off Guided Access if needed.

Use Guided Access on iPad - Apple Support

Use Guided Access with iPhone, iPad, and iPod touch - Apple Support

You are very welcome.