Recently I've started to have an issue with Keyboard Maestro where none of my macros work and I have to restart my Mac to get anything to work again. Restarting the Keyboard Maestro engine from the menu bar app doesn't help either.
Check what it says in your two log files. In the KM Editor you can open the folder by click on the Help Menu / Open Logs Folder. Start with Editor.log, because that's the application that actually starts the Engine. If it fails to start the engine, there will most likely be a text message explaining why it failed.
Thanks, I'll try this next time
Check the Interactive Help (in the Help menu) and see what it reports as the issue.