Additional features, settings, or issues not covered by specific Microsoft Teams categories
This has happened to me a number of times. It seems every time I get a Visual Studio 2019 update I lose connectivity to MS Teams. Various forums have not yielded much answers until I found the solution!!!!
It seems if you are connected to a corporate network (i.e. vpn, etc) Teams can't connect.
The solution is to connect to a non vpn network (i.e. home, coffee shop, tether to your mobile, etc), then start Teams.
Once you do that, you should be able to reconnect to your company's network again.
Microsoft FIX your product!!!