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Best Way To Fix IPhone 4 Error 21

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Over the past few days, some of our readers have come across an error message that says iPhone 4 Error Recovery 21. This issue occurs for several reasons. Now let’s talk about some of them. The most common reason for iTunes error 21 is when iTunes tries to download recovery files (.Ipsw), but unfortunately blocks authentication. This could be due to a hardware failure or communication failure between your device and the servers.

 

 

Learn how to troubleshoot iOS update and restore issues.

Try These Steps First

  1. On a Mac with macOS Catalina 10.15, make sure your Mac is up to date. If you have a Mac with macOS Mojave 10.14 or earlier, or a PC, make sure you have the latest version of iTunes installed.
  2. If the device cannot be restored and the message “An unknown error occurred [error number]” is displayed, try the following.

If the error persists, try the following.

Choose Your Number Or Error Message

Select your fault to find out what to do:

  • one,2, 3, 4, 6, 9, 10, 11, 12, 13, 14, 16, 17
  • 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37,
    40, 53, 56
  • 1002, 1004, 1011, 1012, 1014, 1015
  • 1600, 1601, 1602, 1603, 1604, 1611, 1638,
    1643-1650, 1667, 1669, 1671
  • 2001, 2002, 2005, 2006, 2009
  • 3002, 3004, 3013, 3014, 3015, 3194, 3200
  • 4005, 4013, 4014, 4037
  • Update The Software On Your Mac Or PC

    iphone 4 error restore 21

    If you see error 10, your iOS device may have a newer version of iOS than your computer supports. You need to update the software on your Mac or iTunes on Windows before you can update or restore your iOS device.

    macOS 10.11 and up:

    1. Disconnect your iOS device and reconnect it to your computer. You may need to unlock your iOS device before your Mac can recognize it.
    2. If you find that a software update is required to connect to your iOS device, click Install to download and install the software so your Mac can update or restore Connect your iOS device.

    Windows: update iTunes to the latest version.

    If you’re still getting error 10 or don’t see the dialog box asking you to update the software on your Mac, contact Apple Support.

    Make Sure Your Device Can Communicate With Apple Servers

    If you see error 1671, your computer is downloading the required software. Wait for the download to complete and try again.

    If you encounter any of the following errors, your computer may not connect to Apple servers or to your iPhone, iPad or iPod touch:

      17, 1638, 3014, 3194, 3000, 3002, 3004, 3013, 3014, 3015, 3194, 3200

    • “There was a problem downloading the software.”
    • “The device is not authorized for the requested build.”

    Check the following:

    1. Make sure your computer can communicate with Apple’s software update servers.
    2. Check third party security software.

    If you see error 4037, your computer cannot update your device because the password is locked and the device was not unlocked for updating or restoring. Unlock your device and try again. Find out what to do if you forgot your password.

    If the error persists, contact Apple Support.

    Failed To Update Mobile Phone Or Apple Pay Alert Is Not Available

    If, after updating, you get the message “Cellular update failed” or “Apple Pay requires updating on this iPhone,” please tell me what to do.

    Check Your Security Software

    Check Your USB Connections

    If you see error 4005, 4013, or 4014, follow these steps.

    If you encounter any of the following errors, check your USB connection, USB cable, USB port, or computer:

      13, 14, 1600, 1601, 1602, 1603, 1604, 1611, from 1643 to 1650

    • 2000, 2001, 2002, 2005, 2006, 2009
    • An error containing an “invalid response”.

    Here’s what to check. Please try again after each step:

    1. Use the USB cable supplied with your device. If you don’t have one, try a different Apple USB cable.
    2. Switch to a different USB port on your computer. Do not plug it into a keyboard.
    3. Switch to the USB port on the other computer.
    4. If the error persists, check for other USB issues, check third-party security software, and then check your hardware.

    If the error persists, contact Apple Support.

    Check Your Stuff

    If you seeerror 53, try the following.

    If one of the following errors occurs, there may be a hardware problem:

    • 1, 3, 11, 12, 13, 14, 16
    • 20, 21, 23, 26, 27, 28, 29, 34, 35, 36, 37, 40, 561002, 1004, 1011, 1012, 1014, 1667, 1669

    Here’s what to check. Please try again after each step:

    1. If iTunes is already open, close and reopen it.
    2. Check third party security software.
    3. Make sure your USB cable, computer and network are reliable. Then try restoring your device two more times.
    4. Check for outdated or modified software.

    If the error persists, contact Apple Support.

    Check Outdated Or Modified Software

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    Learn how to troubleshoot iOS update and restore issues.

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