Hi @gregy,
Sorry for the trouble here–let’s see if we can figure this out together.
Have you updated The Events Calendar and the other add-ons to 4.0? Everything should be running 4.0 to ensure full compatibility.
As far as the database goes, you could delete Facebook Events from your plugins folder, reinstall it and no data will be lost from the calendar. That information will continue to be retained in The Events Calendar data, even without Facebook Events. You shouldn’t have to delete Facebook Events to perform the update to 4.0 though.
When you update the plugins to 4.0, please try doing so all at once, either as a Bulk Update in WordPress or manually installing the updates together via FTP. That should help with a smooth transition as well.
Let’s start here and see what we find.
Thanks,
Geoff