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Sorry.
Something must have gone wrong with the upgrade/update as I still have all of my bookmarks organised and the way I left them and my 2015/2016 iPad Pro is running iPadOS 15.7.2.
After ANY iOS/iPadOS upgrade/update, you should ALWAYS perform a simple hard reset/forced restart of your Apple mobile device.
For iPad models with a Home button, do a simple hard reset/forced restart of your iPad by holding down both the Home and sleep/wake/power button simultaneously until your iPad goes to black and restarts with Apple logo, then release the buttons.
OR
For much newer design iPad models, without a Home button, try the new simple hard reset/forced restart procedure for the new 2018-2022 iPad Pros, 2020/21 iPad Air 4 and 5, the 2021 iPad Mini 6 and the new 2022, 10th gen base models,
1. Press and release the volume button closest to the top Power button
2. Then immediately press and release the volume button farthest from the top Power button.
3. Then, press and hold the top single sleep/wake/power button You will see the Slide to Power off button, but keep on holding down the power button until you see the Apple logo, then let it go.
Once you have performed all the steps, wait for a few seconds and your 2018-2022 iPad will boot up completely to the iPad’s Lock screen.
If still no joy, if you have a previous data backup of this iPad, you may need to do complete erase of this iPad and do a restore from backup of this iPad.
Also, you can leave unacknowledged iPad feedback of your iPad issues, directly, with Apple by tapping the link below.
Feedback - iPad - Apple
Sorry & Best of Luck to You!
