Have you recently had the display replaced? When did this issue pop up? Did you buy it second hand and has it always been like that.
There's no real way to fix a broken touch ID sensor. It's more likely that the home button was replaced with a different sensor making it unable to be used woth touch ID since it's not the original sensor
If you got it like that and it wasnt noted id file for a parshal or full refund (if you're willing to return the phone)
If this happened after the display was replaced it means the repair shop or you who did it has put in a new home button that won't towkr with touch ID since it's not the original one that came with the iPhone.
If it just randomly stopped working it could be a software issue but it's most likely a hardware issue and I'd suggest getting the home button repaired by apple or a 3rd party if they can.
Hope this helps