Try this
Attention: You must follow these steps to make the new fingerprint sensor work and also avoid getting error 53 when you upgrade the firmware
1. Always backup your phone's data in iTunes before replacing the screen or do anything.
2. Before replacing the flex cable, go to settings to delete all previous fingerprint data, then turn off Touch ID & any passcode security.
3. Now proceed with the home button flex replacement.
4. After replacing the flex cable, connect the phone to computer, open iTunes, run a backup first then click "Restore Firmware" (not restore from backup). Note that all data will be wiped out on your phone and it will be upgraded to the latest firmware.
5. Now restore from backup to get your data back, or set up the phone as brand new. And you can finally turn on passcode security and set up Touch ID again.