This is a long shot, but is it starting, just not appearing in your main window? (you can tell if it’s running in the Task Manager.)
This may happen if you’ve used a secondary display at some time, e.g. in NVidea “set up multiple displays.” I lost the ATC window (not the main window), but found it when I plugged in my secondary display, and moved it around the sides of the main window. Moving it back to the main display solved the problem.