If you have recently upgraded to Mojave, then that is almost certainly the issue. You will have to ensure you enable Accessibility for both Keyboard Maestro and Keyboard Maestro Engine. If you have any troubles with accessibility (eg typing keystrokes, selecting menus, copy/paste, etc), you need to toggle the accessibility permissions (System Preferences, Security & Privacy, Privacy, Accessibility) for Keyboard Maestro and Keyboard Maestro Engine off and then on again.
There is no need to mess around with Time Machine and such, you can revert to recently past macros with this sequence:
- Quit Keyboard Maestro editor if running
- Launch Keyboard Maestro editor
- File ➤ Revert Macros ➤ pick a date - days available are typically the last seven days you have made changes to your macros).
- Make any tests, export any macros as needed, etc
- File ➤ Revert Macros ➤ At Editor Launch (this is why it is important to quit & relaunch the editor before this sequence, it gives you a solid anchor to revert back to).