If you are experiencing difficulties with TouchID, this support page would be the obvious place to start:
If Touch ID isn't working on your iPhone or iPad - Apple Support
Should you be unable to resolve the problem, you might be best advised to seek assistance directly from Apple Support - and request a remote diagnostic test. 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/gb/app/apple-support/id1130498044