Make sure:
  1. Sign on to your Mac machine. You'll see the Authenticating window and you'll receive a passcode by email.

    Screenshot showing an example of an email with a passcode.

  2. In the Authenticating window, enter the passcode and click Sign On. If you need to generate a new passcode, click Resend Passcode.

    Screenshot of the Authentication window showing the passcode field.

    You'll see the green checkmark indicating authentication is successful.

    Screenshot showing the green "Authenticated" success window.

    You're signed on to your Mac machine.
    A screen capture of the Mac login desktop following successful sign on.