I believe I found a bug in Visio Viewer mobile with Teams. With Visio Viewer mobile installed on a device (I happen to be iOS) and I click on a Visio file in Teams I get a "Cannot Open File" file type not supported. Even if I open Visio Viewer and have it running in background on iOS.
Yet, if I open the Sharepoint Dir. in Visio it will open the same exact file. Seems Visio and Teams don't quite play together right.