I have Visual Studio 2019 16.6.2 installed, along with the .NET Core 3.1.301 SDK and all the necessary Blazor templates.
If I create a brand new Blazor WebAssmbly app
After searching for couple of days, I did the following and it worked like charm:
1.Install IE "Microsoft edge"
2.Use IE "Microsoft edge" as your VS. browser (NOT CHROME)
3.Use your application as server (NOT IIS EXPRESS).
Enjoy.