Can’t enter passcode after IPADOS update

Start here >>> If the screen isn't working on your iPhone or iPad - Apple Support

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

• 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 other iPad models: 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.

Note:  If iPad still 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 will need 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, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/gb/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 test and assess your iPad:

Genius Bar Reservation and Apple Support Options - Apple

Perhaps consider disabling automatic installation of updates - as so doing will mitigate the (albeit remote) possibility of a failed update occurring at an inopportune time.

Settings > General > Software Update > Install iPadOS Updates - set to OFF

In addition to disabling automatic installation of an update, perhaps also consider disabling automatic Download iPadOS Updates. With both options disabled, system software updates can neither download nor install without manual action of your part.

“Sod’s Law” states that if something will go wrong, it will always do so at the worst possible moment.

This isn’t a widespread problem. While you have simply been unlucky - in that something didn’t go entirely to plan during the update - you perhaps need to consider that any system software update is making critical changes to the underlying Operating System.

All system software updates carry a potential risk of something going wrong (this being true of any OS update on any computer). In most cases with Apple iOS/iPadOS, difficulties are usually easily recoverable if you have access to a Windows PC or Mac.

While not being a fix for your immediate problem, perhaps the learning exercise here is to consider where you are when you perform a system software update. If you are away from home - without access to a computer - perhaps wait until you return home; you then have immediate access to recovery tools in the unlikely event that should something go wrong with an update.

Speaking personally, I have three fundamental rules for system software updates…:

1) Perform a backup immediately before attempting a system software update (at the very least using iCloud)

2) Always connect the Power Adapter; do not rely on battery power alone (even with an apparent full charge)

2) Never perform a system software update when travelling away from home

In the past, when travelling internationally, I have delayed installing a critical software update for up to three weeks - as the risk of being without a working iPhone was not feasible. While the update would likely to proceed without issue, the assessed risk was greater than I was willing to accept given circumstances of the time.