This issue happens for a very few users and this can be fixed quite easily. Users should be aware that before every update, the following parameters should be checked properly.
- iPhone is fully charged.
- Device Wi-Fi connection is strong.
- Optimum storage is available for the update.
Step 1
Try ‘Lock & Wake’
Try pressing the power button to lock and wake the device. Repeat this for about 5 – 10 times and check if the update starts progressing. If this issue still persists, move to step 2.
Step 2
Try ‘Hard Reboot’
Hold the 'Home' button and the 'Sleep/Wake' button at the same time until the screen turns off and release the buttons once apple logo appears. This would reboot your device. Once it is rebooted, click on ‘Settings’ > ‘General’ > ‘About’ and make sure the phone is updated. If the phone is not updated, repeat the update procedure. If this doesn’t help, move to step 3.
Step 3
Try ‘Restore and Update’
Take a complete backup of the phone on a computer via iTunes, click the device connected to the iTunes and tap summary and Restore iPhone. This restores the device to the previous state before the issue. Now check for updates for the connected iPhone in the iTunes page. Click ‘Download’ and ‘Update’.