Owners of Apple's iPhone 5s either seem to love its Touch ID fingerprint reader or hate it with a passion. For some people (like myself), it works the vast majority of the time, while other people have told me they've given up on using Touch ID to unlock their devices. Over at Macworld, blogger Serenity Caldwell has written up a nice guide on how to troubleshoot issues with Touch ID and keep your frustrations to a minimum.
To start with, Caldwell suggests that you use a set of good fingerprint scans or if you're having issues, to re-scan your prints. First, adjust your grip on the phone to match what you may do in reality. Many people lay the phone down while doing the scan, and then don't vary the angle at which they are making the initial scans. When they try using Touch ID in real-life conditions, holding the iPhone 5s at an angle, they get bad results.
Caldwell then goes on to point out that you should store more than just one fingerprint in the device. You can save up to five -- I've actually scanned both thumbs and both index fingers, and rarely have an issue with Touch ID. Scanning multiple fingers also helps out in cases where you may have a cut on your normal "scanning finger" that may impede with good results. Finally, Caldwell points out that your finger must touch the metal ring surrounding the Touch ID sensor, as it helps the scanner recognize your print.
So what should you do when Touch ID isn't working correctly for you? Think about the conditions under which you're using it. If your hands are really cold, Touch ID won't see your finger as being warm and conductive, and won't register a print. Likewise, be sure to dry your fingers well before using Touch ID. Water can interfere with scanning, and even having soaked your hands in water for a while will result in a different-looking fingerprint pattern.
Touch ID won't work the first time you try after a restart of your device, if you fail a thumb scan more than five times, if you haven't used it to unlock your phone in more than 48 hours or when you try to change the Touch ID settings. All these are features built into Touch ID to keep thieves from easily hacking your device.
Last but not least, Caldwell recommends that you make sure the Touch ID sensor is clean. Just use a clean cloth to rub it clean, and you should be fine.