Mobile or PC? I'm assuming PC because it's more widely available. In that case, have you tried resetting both your pin code and Windows Hello? When I first set up my laptop, that's what I had to in order to get the finger print working for Windows Hello. Sadly though, you can't re-download Windows Hello because it's baked into the OS.
If you have any more problems, concerns, or are actually dealing with a mobile phone, don't hesitate to make an account and message back!