You may have downloaded the wrong app - Google has a similarly named Duo app that is used for video calls. The Duo App you need for CalNet has a green, square icon and is made by Duo Security, Inc. For reference, this is the app that should be used:
A knowledge base article about My Duo app doesn't have an option to add accounts as detailed in the instructions. provided by the UC Berkeley IT Service Hub - Knowledge Portal
You may have downloaded the wrong app - Google has a similarly named Duo app that is used for video calls. The Duo App you need for CalNet has a green, square icon and is made by Duo Security, Inc. For reference, this is the app that should be used: