How to make your iphone finger print work more reliably

Go to Settings > Touch ID & Passcode

If promoted, enter your passcode

Click Add a Fingerprint

Follow the steps to add your finger print.

Ok, you have added your fingerprint. Normally, you would stop here, but we are going to repeat this process again using the SAME FINGER.

That's it! The more you repeat the process, the more reliable your finger print becomes (you can add up to 5 fingerprints). Enjoy unlocking bliss!