There's a problem if you're using the latest version of this plugin.
Version v3.2.4 of FullCalendar needs at least version v3.2.138 of Filament or it doesn't work. The Alpine JS changes applied in this PR https://github.com/saade/filament-fullcalendar/pull/236 only work if you have a newer version of livewire.
Not sure what the best way to solve this is. Maybe set the min version of filament in composer to ^3.2.138 ?
Anyway, if anybody has an issue where the calendar just doesn't work, lock the version to 3.2.3