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  1. #1


    Member Since
    May 05, 2008
    Posts
    6
    iphone restore impossible. Error 21
    I tried to update the software on my iphone 4S today. It stopped working, & now won't even restore - I get "the iphone could not be restored. An unknown error occurred (21)'

    It's a completely unhacked/jailbroken iphone, & I have the latest version of itunes (10.6.1), & run the latest OS X (10.7.4).

    A bit of googling suggests that it might be firewalls or some such might be blocking the connection, but I don't have one of these.

    Any ideas?

  2. #2

    Ttaylor394's Avatar
    Member Since
    Feb 15, 2011
    Location
    West Virginia
    Posts
    384
    Specs:
    13in rMBP 2014 Yosemite
    what does iTunes say when you plug it into the computer?
    does it say anything?

  3. #3


    Member Since
    May 18, 2012
    Posts
    13
    Quote Originally Posted by Ttaylor394 View Post
    what does iTunes say when you plug it into the computer?
    does it say anything?

    the iphone could not be restored. An unknown error occurred (21)

    Try putting the phone into DFU mode and see if you can restore it.

  4. #4


    Member Since
    May 05, 2008
    Posts
    6
    Unhappy Still getting error 21
    I've tried using DFU mode several times, but keep going round in circles.

    I put the iphone in DFU mode (carefully monitoring the 10 seconds), iTunes gives the message "iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes".
    I click "ok", then "restore".
    ITunes asks me if I am sure, I click "restore & update".
    After a 10 - 15 seconds I get "the iphone "iphone" could not be restored. An unknown error occurred (21)."

  5. #5


    Member Since
    Jan 22, 2010
    Location
    Victoria, BC
    Posts
    20,911
    Specs:
    Mid-2012 MBP (16GB, 1TB HD), Monoprice 24-inch second monitor, iPhone 5s 32GB, iPad Air 2 64GB
    Sounds like what happened is that you started an update but it didn't finish for whatever reason and so in a practical sense you've bricked it.

    You'll need to see an Apple technician to sort that out.

  6. #6


    Member Since
    May 05, 2008
    Posts
    6
    Still getting error 21
    Thanks for the tip, for I really am getting nowhere (other than frustration city)

    Next question: is the resetting of the iPhone to factory settings a straightforward operation for a mac technician? I am outside my home country, so could I just walk in to a mac shop & get it done (ok perhaps a bit of a wait), or is it a more complex operation requiring more time, production of warranties etc?

  7. #7


    Member Since
    Jan 22, 2010
    Location
    Victoria, BC
    Posts
    20,911
    Specs:
    Mid-2012 MBP (16GB, 1TB HD), Monoprice 24-inch second monitor, iPhone 5s 32GB, iPad Air 2 64GB
    No, should be a very straightforward operation. Make sure you go to a genuine Apple retail store OR a genuine Apple Authorised Service Provider (AASP) in whatever country you're in.

  8. #8


    Member Since
    May 18, 2012
    Posts
    13
    I'm curious, since he's outside of the country of purchase would an Apple store from another country offer any type of assistant?

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