touch id never works - i've tried it a ton of times, and it eventually forgets my fingerprints or something, and just stops working... max it works is like 2 we

touch id never works - i've tried it a ton of times, and it eventually forgets my fingerprints or something, and just stops working... max it works is like 2 weeks, then... it's like i'm a new person. I have even tried training the same finger lots of different times, still no luck. And I've tried it on iphone and mac, no go.