Fingerprint

Try these steps, with testing touch ID with each in between step

1. Make sure you have the latest version of iOS or iPadOS.
2. Make sure your fingers and the Touch ID sensor are clean and
3. dry.* For the Touch ID sensor, use a clean, lint-free cloth to wipe off
4. any dirt or debris.
5. Your finger should cover the Touch ID sensor completely, touching
6. the surrounding metal ring. While Touch ID is scanning, you
7. shouldn't tap too quickly or move your finger around.
8. If you're using a case or screen protector, make sure it doesn't cover the Touch ID sensor or the surrounding ring.
9. Go to Settings > Touch ID & Passcode and make sure that
10. iPhone Unlock or iTunes & App Store is on, and that you've enrolled
11. one or more fingerprints.
12. Try enrolling a different finger.

If it is still not working, you need to contact Apple Support for servicing.

See this link for reference

If Touch ID isn't working on your iPhone or iPad – Apple Support (UK)