Like every other update to the firmware, iOS 7.1 brings with it – besides a few major interface changes and performance upgrades – a few bugs in the form of the personal hotspot issue on many iDevices and the TouchID bug on iPhone 5s.
On the iPhone 5s, if you update to iOS 7.1 and end up with TouchID issues, it's a minor bug that can be solved pretty easily with a complete reset of fingerprint settings. Not many users face this issue after the iOS 7.1 update but for the few that do, the solution is actually quite simple.
If TouchID stopped working right, here's what you do:
- Go to Settings → General → Passcode & Fingerprint
- Enter the passcode if you are prompted for one
- Tap on Fingerprints
- You should see a list under the Fingerprints label (number of fingerprints depends on how many you set up previously)
- Swipe left on a fingerprint. Tap on Delete to delete the fingerprint.
- Do this for every fingerprint you have saved.
Once you're done deleting all fingerprints, let's recalibrate new fingerprints for TouchID.
- Tap on Add a fingerprint… and setup new fingerprints for TouchID authentication.
(here's how to add fingerprints to TouchID)
It's recommended that you first add one fingerprint and test it out. If the fingerprint works correctly in unlocking your iPhone 5s or making a purchase (via App Store/iTunes Store), you can proceed to add more fingerprints.
A general reset of this type usually works in fixing the TouchID problem users face after the iOS 7.1 update. But it's not a universal solution. There are the outliers, the rare cases when other things could be wrong.
For instance, it could be a hardware issue where some sensor fails to work/trigger the on-board chip. You will have to take it to the nearest Apple Store to get this fixed.
Also, it helps to make sure fingers aren't damp or even slightly sweaty.