Alarms not showing in BusyCal

BusyCal relies on its BusyCal Menu app extension to issue alarms. This extension gets bundled and installed as part of the main app.

There is a known issue in macOS where at times the wrong extension may get loaded (from another installed copy on disk, or even at times from a Time Machine backup) and due to this, alarms may stop working as the main app is unable to communicate with the menu extension.

To fix this, please follow the troubleshooting steps laid out in this article.