Code Coverage Results periodically gives: Empty results generated

I just ran into this using Visual Studio 2019. The solution was to go to the "Test" menu item in VS and then update the Test -> Processor Architecture for AnyCPU Projects setting from X86 to X64.

This link solved my issue: Issue with Code Coverage in VS 2012

Close Visual Studio 2012, find the .suo file, delete (or rename) it, restart. Worked fine. No idea what is in the .suo file that prevented proper coverage analysis.