Using Fingerprint sensor.
Swipe the finger as per diagram above.
The following actions are incorrect.
The finger was positioned too left (too right). Position the finger to the center of the sensor.
The movement was skewed.
The movement was too fast.
The movement was 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.