Why is the Install Now button in Software Update not working?

Over-the-air (OTA) updates to iOS can be a convenient way to make sure the latest firmware is installed on your iOS device. Sometimes, when restoring from a backup, an OTA update will download but not install right away. The Install Now button can be greyed out and unresponsive.

The error message reading "You can install this update when your iPhone is finished restoring from the iCloud backup" can be displayed, even if your iPhone, iPad or iPod touch has completed downloading apps and other iCloud content.

Some reports have indicated that turning the iOS device off and back on might help, or resetting the device by holding the home and power buttons until reboot. Most of the time, simply waiting for iOS to recognize that the iCloud restore is complete does the trick. Once iOS finishes its housekeeping the OTA update will install.