Anytime a new mobile device is used with Duo, it must be enrolled in SSO. In particular, this is true when changing phones even though the phone number has not changed.
Additionally, devices that use the Duo Mobile app must activate SSO on the device by scanning a unique barcode generated by Duo.
The Duo two factor authentication system can be used with both smart phones and older cell phones and landlines. Each type of device is used differently in Duo.
Smart phones can use push notifications (recommended), a verification phone call, or passcode text messages. The push notification option requires the Duo Mobile app to be installed and activated on the enrolled device.
Older cell phones, non-smart phones, and landlines can use the verification phone call method to respond to a Duo prompt. Some older phones may also be able to receive passcode texts during the Duo authentication process.
It is recommended to have more than one device enrolled in Duo in the event that the primary device is unavailable.
Learn more about using two factor authentication with SSO.
For help enrolling a device or activating the Duo Mobile app, this page lists the SSO Administrators for each system member.
Note that after 10 unsuccessful Duo authentication attempts, the Duo account is automatically locked and can only be unlocked by an SSO Administrator.