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how to fix error 21 when restoring

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How to avoid the error 21 to restore the iPhone

How to avoid the error 21 to restore the iPhone
 
 Thanks to the comment of Nina in one of our manuals to unlock the iPhone, we show another possible solution to solve one of the many errors that can be found in iTunes when trying to restore your iPhone with a modified firmware.
 
 In this case, the error is 21, and which is caused by a process called iTunes iTunes Helper. To avoid this we must open the Activity Monitor application, as shown in the above image, select it and click Quit Process. It is also desirable before putting the iPhone into DFU mode and start the restoration have closed iTunes.
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  • Make sure you are connected to your computer with an administrative account. If you are unsure, log off and then log on with an administrator account.
  • Upgrade to the latest version of iTunes on your computer by clicking the iTunes menu "help" and selecting "Check for Updates". If you do not see the Help menu, press "Ctrl-B" key on the keyboard to display the menu bar.
  • Windows Update. If you do not have automatic updates enabled Windows by default, install updates manually. Press the "Windows" from the Home screen key, select "Settings, then" Change PC settings. "Select" Update and recovery "followed by" Windows Update ". Click" Check Now. "If there is an update available, follow the onscreen instructions to install it.
  • Confirm that any security software installed on your computer is updated. Windows security software is updated when a Windows update is done.
  • Disconnect all USB devices connected to the computer except the keyboard and mouse. Examine the lightning iPad cable to ensure it is in good condition and reconnect it to a USB port that is known to work properly on your computer.
  • Restart your computer and iPad. Launch iTunes and try to update or restore iPad.

Testing network connectivity iTunes

  • Launch iTunes and select "Run Diagnostics" on the Help menu.
  • Select "Testing Network Connectivity", "Device Connectivity Tests" and "testing device synchronization" by clicking on the checkboxes. Clear the check box "Analysis of CD / DVD Drive".
  • Click the "Next" button. Follow the instructions on screen and click "Next" again. For example, iTunes asks you to confirm your computer is connected to a network before the test begins.
  • Read test results when they appear after several seconds the screen. Items with a green status light are working well. Any item with a status light red or yellow needs attention.
  • Click the "Help" button that appears next to the items marked in yellow or red and follow the instructions on the screen. For example, if Windows Firewall is blocking access to the Internet, the online instructions guide you through opening access to iTunes.
  • Restart the computer and iPad and try to update or restore the iPad twice. If the error persists, contact Apple support or your nearest Apple store.
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