New Teams Application - Files Not Following Default

Our IT Department forced a switch to the new Teams. The old Teams worked just fine. Files in the new Teams won't open in the app by default but open in the browser instead. I noticed this behavior when trying the new Teams, so I switched back to the old Teams.

I suspect it has something to do with the relationship between the desktop app and the browser. When I try to manage the default, it switches to the browser which suggests I open it in the Teams app. When I follow the prompt to redirect back to the Teams app, it can't do it. So there's no way to even check or manage the default behavior. Since the old Teams works on my PC, and the new Teams doesn't, I doubt it's the installation, but rather a bug in the new Teams.

My IT Department isn't likely to fix it on their own unless I tell them exactly what to fix. First, is this something they can fix? Second, if they can fix it, what (precisely) do I tell them to fix?