Do * # * # 6 4 8 4 # * # * and enter the test menu. Click on the 3 dots on the top right and additional tools too. There is fod fingerprint calibration at 11, click on it and before starting the test, put a mirror on the white place where the sensor is, after completing the test, then put something black on the white place. The fingerprint will come back after the test is over. It did not add fingerprints on my head, I solved it with this method, but the fingerprint does not read as before, maybe because I could not calibrate well