Using Fingerprint sensor.
Swipe the finger as per diagram above.
The following actions are incorrect.
The finger is positioned too left (or too right). Position the finger at the center of the sensor.
The movement is skewed.
The movement is too fast.
The movement is too short.
Note: Fingerprints may not be recognized after one scan. There are many situations, just like skewed movement, too fast or short movement, finger strength and so on which may affect the fingerprint sensor.