My fingerprint sensor won’t work anymore

Are you suggesting that the TouchID sensor doesn’t work at all - or just for authentication?

The iPad User Guide describes the straightforward process of setting-up TouchID:

Set up Touch ID on iPad - Apple Support

After registering fingerprints, while still in the TouchID settings page (Settings > TouchID & Passcode) you can test that your registered fingerprint is recognised by the sensor. Just place your registered finger on the TouchID sensor; the fingerprint should be recognised, to which the iPad will respond by highlighting the registered biometric.

If the TouchID sensor is completely inoperable, you won’t be able to successfully register fingerprints at all. If TouchID doesn’t work, refer to this support page:

If Touch ID isn't working on your iPhone or iPad - Apple Support

By default, TouchID will be used as an available alternative to entering your iPad Passcode - although you can alter some settings that will disable or enable TouchID for some authentication tasks. If the TouchID sensor has been demonstrated to functional (as described above), check your iPad settings to ensure that you have not disabled TouchID authentication:

Settings > TouchID & Passcode > [Use TouchID For] 

• iPad Unlock
• Wallet & ApplePay
• iTunes & App Store 
• Password AutoFill
• Other Apps (these will only be listed for Apps that are compatible with TouchID)

If all settings are enabled as expected, try a forced restart - as this will often clear an isolated software issue:

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.
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. When the Apple logo appears, release both buttons.

If the problem persists after performing the restart, it may be necessary to reset your iPad settings. While this reset will not cause any loss of data, as a precaution, it is always wise to ensure that you have a current iCloud or iTunes backup before performing the reset:

How to back up your iPhone, iPad, and iPod touch - Apple Support

When you are happy to proceed, you can perform the reset from iPad settings:

Settings > General > Transfer or Reset iPad > Reset > Reset All Settings

If the problem still doesn’t clear, you would 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 and perhaps easier, 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/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

might be a problem with the home button. When was the last time it worked?