Error 21 is one of common errors when it comes to restore your iPhone/iPad. This happens when iTunes checks the authentication of the .IPSW file or users use old iTunes versions that are not supported by Apple. Here are some simple solutions to fix error 21 on iPhone/iPad
7 ways to fix iPhone/iPad Error 21
Solution 1: Restart your iTunes
Sometimes, the error can be solved by restarting the iTunes. Simply shut down your iTunes, and open it again.
Connect your device with your computer, and take a look to update once more. Now, the error 21 on iPhone/ iPad is resolved.
Solution 2: Update your iTunes
On every occasion, if you want to restore or update for your device, make sure that you have the latest version of iTunes installed on your computer.
For Windows users:
- Open iTunes.
- Open menu bar, and choose Help.
- Choose Check for updates.
For Mac users:
- Open the program.
- Open the menu, and click iTunes.
- Select Check for updates.
Solution 3: Turn off anti-virus programs
In many cases, the anti-virus program that is installed in your system could cause numerous errors, including the error 21. Close your anti-virus, and update your device once again.
Solution 4: Remove unnecessary USB devices
Make sure to disconnect all the devices you do not use from your laptop. Presumably, a number of those devices can affect the restore process; cause the errors 21 for your iPhone/iPad.
Solution 5: Check Sensor cable
It is quite difficult; however, if you know a little about hardware, you can fix this error. Just open your device, and remove the screw that is used to connect the battery. You will see a device cable, merely disconnect it, and then place it back.
Solution 6: Recovery mode
Step 1: Long- press the Power button for a few seconds and make sure to connect your iPhone/iPad to your Mac/PC before performing this task. You will see a popup ‘slide to power off’. Slick it to power off your iPhone.
Step 2: Now press the Home button, then Power button at the same time while holding home button.
Step 3: Past at least 10 seconds, release the Power button, but keep holding Home button until iTunes pops up with a message ‘an iPhone in recovery mode has been detected’.
Step 4: once you are in DFU mode, your iPhone/iPad screen is black.
Now the error 21 has been fixed, you can restore .IPSW firmware without errors.
Solution 7: Check outdated software
You might see the message “The obligatory resource cannot be found.” The error could happen if you are in instances below:
- The version of iTunes is out of date. You have to install the newest version of iTunes, then try to restore or update once more.
- The device is running a beta version of iOS.
- You are attempting to install a previous version of iOS
- Your device has unauthorized changes created to iOS, as “jailbreaking.”
You can use the recovery mode to restore your device to the newest version of iOS.
Above are the best seven ways to mend iPhone error 21 that you can try on your own. If the error still remains, you should contact with Apple to get the best solutions for the error 21.