You can choose to receive the codes by text message or automated phone call. If you're already using two-factor authentication with your Apple ID, you can't turn it off. Then tap Upgrade Account Security and follow the onscreen instructions. Tap Continue when you see a prompt to upgrade account security. Answer your security questions, then tap Continue. Enter a trusted phone number, a phone number where you want to receive verification codes for two-factor authentication (it can be the number for your iPhone). On the web: Go to and sign in with your Apple ID. It ends in FF and still FF after a reboot even with the trick. Tap Turn On Two-Factor Authentication, then tap Continue. My problem is after a reboot, the SystemId displayed in IOReg did not change.
I satisfy all the conditions but still won't work for me so I had to the SystemId trick.
