Microsoft Team Screen Sharing not showing up on Mac OS Catalina - Remote Desktop (Horizon)

We have an end-user having an issue with Microsoft Teams, he utilizes Remote Desktop to do most of his drawings and utilizes Microsoft Teams on his local machine to make video calls and share his screen during meetings. 

The issue is that he is not able to share the screens from the Remote Desktop, they are just not available to select and share. We attempted to review permissions on the mac for Teams, and it has full permissions to launch, screen share, and everything.

I attached a screenshot to give you a better idea of what I'm looking at. 

We also tested this on the Microsoft Teams Web app, and we are also not able to see the Remote Desktop (horizon client) window as an available screen.

Thank you,