my iphone 6s error 3

Check for hardware issues

Errors: 1, 3, 11, 12, 13, 14, 16, 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 53, 56, 1002, 1004, 1011, 1012, 1014, 1667, or 1669.

Your device or computer might have a hardware issue that stops the update or restore from completing.

1. Check that your security software and settings aren't blocking your device from communicating with the Apple update server.
2. Then try to restore your iOS device two more times while connected with a cable, computer, and network you know are good.
3. Make sure that your security software and settings are allowing communication between your device and update servers.
4. If you still see the error message when you update or restore, contact Apple support.

If you still see the error message, check for outdated or modified software

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Check for outdated or modified software

Errors

: 1015. You might also see the message "The required resource can't be found."These errors might appear if any of the situations below are true:

• Your version of iTunes is out of date. Get the latest version of iTunes, then try to update or restore again.
• Your device has a beta version of iOS.
• You're trying to install an earlier version of iOS (downgrading).
• Your device has unauthorized modifications to iOS, also called "jailbreaking."

Use recovery mode to restore your device to the latest version of iOS.