iPad stuck on white screen with Apple logo during software update

If your iPad is unresponsive, connect your iPad to its Power Adapter and allow the iPad to charge. Then, while still connected to external power, try a forced-restart:

Force restart iPad (models with Face ID or with Touch ID in the top button)

If your iPad doesn’t have the Home button, do the following:

1. Press and quickly release the volume button nearest to the top button.
2. Press and quickly release the volume button farthest from the top button.
3. Press and hold the top button; do not release the top button until...
4. When the Apple logo appears, release the top button.

Force restart iPad (models with the Home button)

• Press and hold the top button and the Home button at the same time; do not release either button until...
• When the Apple logo appears, release both buttons.

When performed correctly, your iPad will restart.

If iPad doesn’t turn on, or if it gets stuck during start up, see the Apple Support article If your iPhone, iPad, or iPod touch won’t turn on or is frozen. Or if your iPad isn’t working correctly after you restart it, see the iPad Support website.

If you continue to experience difficulties, you might be best advised to seek assistance directly from Apple Support. You can contact the Support Team using the Support link at top-right or bottom-left of this page. Alternatively you can initiate and manage your support cases from Apple devices using the excellent Apple Support App. If not already installed, the App can be downloaded from the App Store:

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

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

Genius Bar Reservation and Apple Support Options - Apple

Lumifer wrote:

My ipad is stuck on the update screen and I can't force shutdown it no matter how long I hold the power button.

forced restart:

1. Press and quickly release the volume up button.
2. Press and quickly release the volume down button.
3. Press and hold the side button until you see the Apple logo (this might take longer than 10 seconds), and DO NOT SLIDE TO POWER OFF.

The operative word here is QUICKLY for the first two buttons, then a long hold for the SIDE button; and try it a couple of times, the timing is a little tricky. If done correctly this will always work unless the phone has a hardware problem. 

Try any of the following suggestions:

• If your device appears on your computer, you can configure sync options, and you can sync content, the process is complete. Leave your device connected to your computer and wait for the migration process to finish.
• For over-the-air updates, ensure that the device is connected to a power source to prevent it from running out of power during the update.
• If the update seems stuck, pressing a button may help; if an 'updating' message appears, the update is still ongoing.

Apple logo with progress bar after updating or restoring iPhone, iPad, or iPod touch - Apple Support