FYI:
6.0.2.96 has bug with tray icon... regardless of settings, only shows "stoplight" icon...
I tried 6.0.3.1B and it appears to be fixed in the newer release!
That indicates the core engine (processgovernor.exe) is not running. Why it wasn't running I don't know. It may be something specific to your PC, such as a false positive by security software that caused a quarantine of the executable. This would explain why the new version resolved it, since the file changed. However, that's a wild guess.
Thanks for the analysis...
I will be on the lookout in case it recurs in future releases!