Log in to the My Cal Poly portal. Go to the Personal Info tab > Personal Info > Authorized Devices > Multi-factor Authentication > click Edit.
Image ModifiedClick Other Options.  You’ll be prompted to authenticate now, do not respond to it. Wait until step #6 to authenticate instead. Select Manage devices. This is located at the bottom of the list.  Choose the phone number you wish to reactivate from the drop-down list, then select an authentication method and complete the verification on your currently enrolled device.  Once authenticated, you will see a page that lists your devices in square cells. 
|