Millions of queries were found on the internet regarding error 21 occurring in PC. People come across this error when they try to upgrade or restore their iPhone. The error shows the following description:
Error 21: The iPhone could not be restored. An unknown error occurred.
No need to get upset if you’re getting this error on a frequent basis. This article contains the step-by-step instructions used to resolve error 21 instantly.
- Enter into DFU Mode
- Use ZiPhone Application
- Modify Hosts File
- Use TinyUmbrella Application
- Reinstall iTunes