Screen optical fingerprint malfunction usually occurs after replacing the screen assembly, fingerprint module, disassembling the device, or applying/removing a screen protector. You can try the following methods to resolve the issue:
Prepare a set of fingerprint calibration weights, which are rubber blocks with evenly engraved vertical lines, typically flesh-colored or black. Some people have successfully used a regular eraser wrapped with a rubber band as a substitute calibration weight.
Go to "Settings" -> "My device" -> "Detailed info and specs," and tap "Kernel version" repeatedly until you enter the CIT interface.
In the CIT interface, tap the three dots in the top-right corner, then click "Additional tools." click "Fod fingerprint calibration" and tap "start." Follow the on-screen instructions to complete the calibration using the calibration weight.
Note: Calibration will erase your previously registered fingerprint data.
If you are unable to complete the calibration successfully, you may need to replace the optical fingerprint sensor.
If you're using a third-party screen, the fingerprint functionality may not work, especially if the screen uses LCD technology instead of OLED. LCD does not support optical under-display fingerprint sensors.