The KM Editor Won't Open on macOS El Capitan

Questions & Suggestions
1

For the past few days (perhaps since upgrading to El Capitan 10.11.6?), the Keybard Maestro editor won't open on my Macbook Pro (Late 2011).

When I try (either from the Applications folder, the Dock, or the KM engine mac menu-bar menu, nothing happens.

Thinking it might help to restart the KM engine, I quit it from the drop-down menu. But no change.

Any idea what I can try?

Thanks!