Having trouble signing into iTunes or the new App store using your Apple ID? Get an annoying “MZFinance.NoGUIDTokenFailureKey_message” error message? Still won’t work after you reset your password? Join the club. We’re mostly MacBook Air users here.
The simple solution will delete all of your current network preferences — so make sure you have all that information on hand to re-establish your network connections afterwards.
Delete the file “NetworkInterfaces.plist” located at …
*The name of your hard drive may be different, adjust accordingly
Don’t just set “NetworkInterfaces.plist” aside, move the file into the Trash — you’ll need an Admin password to do this. No need to empty the trash for now, in case you may want to recover it. Don’t forget to reboot your MacBook Air before testing.
Suggested link Apple Support Forum’s Topic : Error Logging in to store
Answers the question How to fix the MZFinance.NoGUIDTokenFailureKey_message error on signing into the Apple Mac App Store?