Clean the Button and Finger:

Moisture and oils prevent accurate reading. Dry your finger and wipe Home button with soft cloth.

Re-register Fingerprints:

Settings > Touch ID & Passcode. Delete existing fingerprints. Register new ones slowly and precisely.

Register Multiple Angles:

Register same finger twice from different angles. Or register multiple fingers. Improves recognition success.

Restart Device:

Temporary software glitch may disable Touch ID. Restart iPhone or Mac and try again.

Update iOS/macOS:

Updates fix Touch ID bugs. Ensure system software is current.

Reset All Settings:

Settings > General > Reset > Reset All Settings. Doesn't delete data but resets system preferences.

Conclusion:

Cleaning and re-registering solve most issues. If all else fails, hardware damage may require repair.