If you see this message when attempting to update your iOS, the iPhone activation server is temporarily unavailable, and iTunes has not yet updated your iPhone.
You can disconnect iPhone from your computer and continue using it with the currently installed iOS, and then try again at a later date.
In rare instances, you may experience an error -4 message in iTunes, and on iPhone you may see a Connect to iTunes screen. If this occurs, make sure iPhone is connected to your computer. If the Connect to iTunes screen does not go away, try the following:
- Disconnect iPhone from your computer.
- Wait five minutes.
- Reconnect iPhone to your computer.
- Open iTunes if it doesn't automatically open.
If the issue persists, follow these troubleshooting steps.