I keep getting 'Unknown Error occurred 21' while trying to restore

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I keep getting 'Unknown Error occurred 21' while trying to restore

It started with the apple logo just flashing on and off. So I went to reset my daughters iPhone by pressing the on/off button and the menu button simultaneously until the iTunes logo and the USB cable was shown on the screen. At that point, iTunes wrote;

'iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes.

I clicked 'OK' and then 'Restore'. ITunes then went on by 'extracting software...' for a minute or two and then 'Preparing iPhone for restore...' The apple logo was then shown on the iPhone and a message box i iTunes;

'The iPhone 'iPhone' could not be restored. An unknown error occurred (21)'

The message box leads to 'More Information' that says that the error 21 ' typically occur when security software interferes with the restore and update process'

That's it. I have tried everything. (I think);

Checking for iTunes updates

Checking for OS (Win7) updates

Restarting the computer

Changed the USB cable

Changed the computer

Ensuring that I have administrator privileges and that iTunes has it as well.

Disabling the antivirus

Disabling the firewall

If you have any advice, please let me know.

Regards

Torben Busk

iPhone 4, Windows 7

Posted on Apr 22, 2012 12:54 PM

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Answer 1

Apr 22, 2012 2:40 PM in response to Torben.Busk

Have you tried the steps here?

TS3125 will help with anything security related.

If none of the steps work, i'd recommend reinstalling iTunes.

Removing and reinstalling iTunes, QuickTime, and other software components for Windows Vista or Windows 7.

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Answer 2

Torben.Busk Author

Level 1

0 points

Apr 23, 2012 12:57 PM in response to ThatguyfromThatplace

Thanks for helping out, but I already tried these steps.

I even tried this on a iMac with similar results. The only difference was that the errorcode was called 2001 instead of 21.

Today I took the phone to www.iphoneambulancen.dk. A guy (in Aarhus, Denmark) that specializes in iPhone repairs. I figured, that given his occupation he'd seen most errorcdes. Two hours later, he called me back, and told me that he had replaced the battery.

So, it turns out that a broken battery can cause this behaviour.

But thanks again 🙂

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Answer 3

May 12, 2012 12:04 PM in response to Torben.Busk

Hey guys, after reading the posts and how this could be a problme with the battery, I set out to test and investigate this claim.

What worked for me was I took off the back plate and disconnected the battery from the iphone. The battery looked intact (no leaks or signs of damage), so I just replaced the same battery and turned the phone back on. It allowed for me to do a restore, and I was able to back up all my info from the cloud.

Hope any one else who has this problem has just an eaasy of a time fixing theirs as I did.

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Answer 4

emdad

Level 1

4 points

Jul 18, 2012 6:00 PM in response to Fattycoats

Took the battery out and it restored fine, really stupid i think

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Answer 5

Sep 6, 2012 7:56 PM in response to Torben.Busk

Hi

I had the same issue, I replaced the battery then it allowed me to restore from my backup. However, One day later I have the issue again. Could please share your experience after fix it or share any one have clue to fix this issue.

thanks in advace

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Answer 6

Nov 4, 2012 8:35 PM in response to hareen_niley

I was getting the exact same error while trying to restore my iPhone. I was able to fix it by using reds0w to do the restore.

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Answer 7

YTHGM

Level 1

4 points

Jan 4, 2013 7:33 AM in response to Torben.Busk

I removed the battery and put it back again. Then the problem was solved. My iPhone is back to normal.

If you have this problem, you can try it. Good luck.

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Answer 8

Jun 24, 2013 7:50 AM in response to YTHGM

what if i have an ipod? what do i do?

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Answer 9

Thona

Level 1

1 points

Jun 13, 2014 5:40 AM in response to Torben.Busk

Dear Sir,

Last night, I got the same problem as what you described here. But following your instruction, my iphone 5 iOS 7.0.6 is not solved. Is there another way to solve it beside taking off the battery? I know I'm not a engeenering or repairer, I could not do that.

Thanks,Thona

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