KM has often just frozen up when I restart my Mac (have KM set to launch at startup), and I'd just right-click it from the dock and see "Application not responding", so I force quit it. Then I click again and it would be fine. However, lately it will not start up at all. No amount of force-quitting or restarting will fix it. I've tried re-downloading and starting with a fresh copy of KM, but it will not launch. Well, it won't get past launch anyway. The Keyboard Maestro menu items appear, and then the spinning beachball appears when I try to mouse over them. No amount of time will get it past this point. But if I click on any other application or even the Finder, I can't get the KM menus to reappear until I start the process over. Activity Monitor recognizes that it is "Not Responding". I read another thread with this problem, and they suggested checking the Library/Application Support/SIMBL folder, but that is empty. I even trashed that folder just to see if it would make a difference. Still can't get KM to start. I typically use KM daily with about 6 macros, not heavy at all, mostly just typing common phrases, etc. Mac Studio running current macOS 13.4.1 (c). I have had this issue for a couple months now. Help!
It might not be your issue but it's something you can try. I had a similar issue years ago. I had some corruption within my Login items process. Try deleting all of the items, in your Settings/Login items area, and slowly add the most necessary items back (starting with the KM engine). See if that assists with your issue.
KC