What can I do if my Touch ID won't enable on my iPhone

Hi, you can check this: If Touch ID isn't working on your iPhone or iPad

If the issue persists, you can bring your phone to the Apple Store or Apple Authorized Service provider. You can book an appointment on getsupport.apple.com or use the Apple Support app.

That depends, on where you are located.

Check this link to find out about your local service options:

Apple - Find Locations

Did you already try the general troubleshooting, mentioned in this article?

If Touch ID isn't working on your iPhone or iPad - Apple Support

Has the Home Button been replaced? If yes, only Apple or an Authorized Apple Service Provider can pair the Home Button to the phone again, to regain the Tuch ID function.