Touch ID not working

Hello there guys I recently bought an iPhone 6 off eBay which was smashed screen and when I received the item I see the Touch ID keeps saying Touch ID can't setup on this phone I contacted the seller he said it was working fine b4 but if I replace the LCD screen it will work back again so I decided to replace the LCD and keep the original metal shield and home button so the Touch ID will work but after I replaced it I see the Touch ID not working still saying the same thing can't setup Touch ID on this phone so I'm quiet frustrated do u guys have any solution for it? Any answer would b appreciated .thanks