I Installed Unity 2019.2.0f1 (latest stable) and VS 2019 via the Hub install on Windows 10. I have no previous full VS versions installed, but I do have VS Code.
The symptoms of issue was that the script would open from Unity in VS 2019, but advanced error checking/auto-complete was not working (though auto-complete was working in a limited fashion). In addition, the Solution Explorer was showing 0 projects.
The current advice is to downgrade to VS 2017 due to compatibility issues between Unity and VS2019, however I fixed this by updating the External Script Editor in the External Tools in Unity (as suggested by the video).
The slight hitch was that Visual Studio 2019 was NOT in the drop down of available editors, so I had to ‘Browse…’ for the application manually and work out where it was (\Program Files (x86)\Microsoft Visual Studio\2019\Community\Common7\IDE\devenv.exe" for the standard 32-bit Windows install).
As soon as you select the application exe in the browse dialogue, Unity recognises it. I then opened a script from Unity in VS2019, and all is working as it should, error checking is on and the project is in the Solution Explorer.
Hope this helps!
