1. Please register all sides of your finger while adding your fingerprint. Make sure there is no liquid or other material between the sensor and finger when trying to unlock the device. Wipe the scanner with a clean cloth regularly. 2. Try pressing firmly and if that doesn’t work, try pressing very lightly. If the scanner still doesn’t work, please try restarting your device. 3. Make sure your device is up to date, delete all the fingerprints and register them again.