If you change your screen and the fingerprint sensor doesn't work very well (e.g. you get a message "Couldn't add fingerprint. Try again") or if the sensor doesn't work at all, follow these Instructions to calibrate the sensor and after that, it's gonna work even better than before. You may need to do the tests more than one time since they may FAIL. The screen must be very clean. You only take the white and black paper/cloth off the screen ONLY when every test is finished! Remember that when you pass all the tests, you REBOOT the phone, you don't just go back to the main menu. If you follow exactly the instructions you gonna have 100% success.
