Why is my fingerprint not work

@danielmohamed first make sure that you have the latest software updates download. You do that by Settings > About Phone > Software Updates > Download and Install > and check theere. If nothing is to be downloaded you have the latest software.

Next you want to try and check and add fingerprints. I have a feeling that this will not work on your phone. From Settings, tap Biometrics and security, and then tap Fingerprints. Enter your secure screen lock credentials. Tap Add fingerprint. Follow the on-screen prompts, and then tap Done.

Now, you can try and clear your cache.

• Turn-off your phone.
• Plug in the USB cable via PC or Type-C earphones (in case its USB-C to USB-C).
• Then press and hold Power and Volume up buttons.
• Release the power button. When the recovery screen shows up, release the volume up button.
• Navigate to and select Wipe cache partition (Volume up and down is for highlighting options and power is to select).
• Navigate to and select Yes.
• Press the power button to select Reboot system now.

I suspect that this still will not make the sensor work. I suspect this to be a bad sensor. For that you will have to disassemble your phone and most likely replace the Fingerprint Sensor flex cable. Since iFixit doesn't yet have a guide for that, use something like this video to work on it.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!