Some of you may have tried to download updates from App Store, only to receive a message “Your device or computer could not be verified. Contact support for assistance”.
Solution is to delete network preferences file, which will then get recreated after restarting the computer.
1) Make sure you are logged in as the administrator
2) Open Finder and go to /Library/Preferences/SystemConfiguration
3) Delete file NetworkInterfaces.plist (back up the file first for just in case)
4) Restart your Mac
5) After restart, go to App Store and the error message should be gone