What's Fixed
GPM and release ZIP installs no longer require a manual composer install on the server.
Production Composer dependencies (sabre/vobject + optimized autoload) are now included in the package. Without them, OpenCalendar exited early with “not ready”, so sync and shortcodes did nothing.
Upgrade
bin/gpm update opencalendar
bin/grav cacheOr reinstall from GPM / this release ZIP, then clear cache. No Composer step needed.
If you already ran composer install as a workaround, updating is still fine.
Full Changelog: https://github.com/TimUx/grav-plugin-opencalendar/blob/v1.3.1/CHANGELOG.md