If you have a U2F configured fob as a Duo device, you will see the following message after entering your NinerNET username and password when you attempt to login through the university's single sign on:
To authenticate...
Using your fob: insert your fob into a USB port and pinch the activation button
You will not be able to select the "Remember me for 30 days" option when using the fob.
Using another Duo device: click Cancel and select the alternate device from the Duo device dropdown menu