An issue I am talking about here occurred in September 2019. I don't know if Microsoft has fixed this problem.
When I installed Visual Studio 2019 on a machine, I was prompted to restart the computer. After I restarted my computer, I tried to open VisualStudio but I saw an error message:
Cannot run when setup is in progress.
I realized that Visual Studio may not be completely installed, there may be some related processes running. So I checked the Task Manager, and found that there was a process called VSIXAutoUpdate.exe running, and it seemed that it was not installing any other things, but it might take up some Visual Studio resources so Visual Studio could not run.
After I stopped VSIXAutoUpdate.exe, Visual Studio 2019 could be opened normally.