Q: trying to upgrade from 4.0 to 9.1 keep getting error 9

Check your security software

Errors: 2, 4, 6, 9, 1611, 9006.

Sometimes security software can stop your device from communicating with either the Apple update server or with your device.

Check your security software and settings to make sure that they aren't blocking a connection to the Apple servers.

If you still see the error message, check for USB connection issues.