1. Make sure that airplane mode is off (Settings > Airplane Mode) because you must have a wi-Fi connection to start your backup.
2. Make sure that is connected to Wi-Fi.
3. if "Restrictions" turned on in Settings > General > Restrictions; tap Settings > General > Restrictions > Accounts and set this to Allow Changes.
4. Reset the network settings (Settings > General > Reset > Reset Network Settings).
5. Update your iOS device (Reset the network settings by tapping Settings > General > Reset > Reset Network Settings)
6. Make sure that you have enough memory left on your phone.
Tap Settings > General > About > Available, and make sure that you have at least 50MB’s available.