Your problem is Catalina, not the other way around. I found this out when I upgraded from El Capitan then everything when to hell real quick. Most everything quit working. Then I down graded to El Capitan and everything returned to normal. I don’t like the path Apple has chosen. The upgrade is designed to work only on late model computers. Not on everything like it used to be. I get what’s going on. It’s about greed. Apple is betting your going to run out and buy a new computer or an iPhone or anything else that creates revenue for them. They don’t care about us. their faithful followers, Like I said it’s al about the money.
I’m about to do a new sometime release during this week. But I did not tackle this specific issue. I have to make some effort to try to reproduce it here on my dev machine.
Some other user described his problem over an email and helped me to reproduce the issue here.
TotalFinder’s Dock icon stops opening new TotalFinder window if you previously had a TotalFinder window with multiple native Finder tabs and closed it. Not sure why is this happening, probably one of Finder’s tabs stays in some weird state and clicking the Dock thinks it is still on-screen so it does not create a new Finder window. Something like this.
Anyways, a workaround is to force-quit Finder.app via CMD+OPT+ESC and launch /Applications/TotalFinder.app again. To prevent this situation in the future, please makes sure you have unchecked
Finder -> Preferences -> General -> "Open folders in tabs instead of new windows"