when I create a calendar event and add some attendees (by e-mail) no invitation is sent.
E-Mail and the groupware setting is properly configured (and working). I am not using shared calendars.
I am using Nextcloud 19.04, but the issue was also present with Nextcloud 18.x
I too am experiencing this bug. Invitations work in some cases and not in others.
Also I notice that If I update an invitation to someone that has received a calendar invite (e.g. add a link to Jitsi), it does not update on their end. The same seems to be true for subscribed calendars - an update in NextCloud does not appear on the subscriber’s calendar.