Touch ID failed problem for iphone 6

So usually when you get a screen replacement from someone they fail to replace the original LCD which includes the flex cable for touch id. Well my touch id wasnt working for the longest and i recently found out why. so i didnt the lcd replacement myself and it worked. like the sensor works and it doesnt say unable to recognize touch id. and when i double tap the home button it works too. but when i go in to set my fingerprint it says touch id failed...any ideas on why thats happening? i was thinking maybe i should update to the latest ios...but besides that anything else?