HT201413: Resolve issues between iTunes and third-party security software
Learn about Resolve issues between iTunes and third-party security software
Q: Error 21? what is it and why
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May 8, 2014 12:49 PMby mario49,Hey DeePatty,
Thanks for using Apple Support Communities.
Resolve specific iTunes update and restore errors.
http://support.apple.com/kb/ts3694#10
Check for hardware issues
Related errors: 1, 3, 10, 11, 12, 13, 14, 16, 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 1000, 1002, 1004, 1011, 1012, 1014, 1667, or 1669.
Try to restore your iOS device two more times while connected with a cable, computer, and network you know are good. Also, confirm your security software and settings are allowing communication between your device and update servers. If you still see the error message when you update or restore, contact Apple support.
Error 1015 might happen after making unauthorized modifications to iOS, also called "jailbreaking."
Have a nice day,
Mario
