Studio 2019 doesn't load files from SDL Server

I have a client whose projects I have to access through SDL Server, and it’s not working with Studio 2019.  I wonder if someone has any ideas.

 
I work on a Mac with a Windows virtual machine in Parallels Desktop.  Generally, this arrangement doesn’t cause any problems with Windows, and if I have a problem, people running Windows native on a PC almost always have the same problem.  So blaming it on the Mac is almost always a false conclusion.
 
Here’s how it’s been (not) working:
 
Working from the Mac side:
 
1.  I click on the client’s server link in an e-mail on the Mac side.  This opens a browser window and asks me to select an app to open the connection with.  In Studio 2017 and before, this would open Trados and start the process of downloading the project (i.e. show me the dialog boxes).
 
However, with Studio 2019, this just opens Trados (sometimes two instances at the same time), and the process of downloading the project never starts.
 
Working directly from Windows:
 
1.  I click on the client’s server link in an e-mail. This opens a browser window.  However, the browser gives me an error message stating that the link leads to an insecure site that may contain viruses.  I click “OK”, Trados never launches, and of course, the project never downloads.
 
This happens in both Firefox and Chrome.
 
In the Microsoft Edge browser, I get an error message saying that I need a specific SDL app to make the connection, and to search the app store for it, but the app doesn’t exist in the store.  Trados never launches, and of course the file never downloads.
 
Any ideas?