Dear Samsung Member,
Greetings from Samsung Customer Support!
Please perform the below mentioned steps to resolve the issue:
1) Ensure that the screen protector or the touchscreen on the fingerprint recognition sensor area is not scratched or damaged by objects, such as coins, keys,pens,and necklaces.
2) If you bend your finger or use a fingertip, the device may not recognize your fingerprints.Press the fingertip so that your fingertip spreads over the wide surface of the fingerprint recognition area.
For further assistance, register your concern in Samsung Members Application (Open Samsung Members Application > Get help > Send Feedback > Error report/Ask questions).
Thank you for writing to Samsung.
Samsung Customer Support