Invites not sent in shared calendars

[Perdex]

Steps to reproduce

1. Open Nextcloud Calendar in the browser
2. Create a new calendar
3. Create a new event in that calendar (using the non-minimized editor)
4. Add an email as an attendee
5. The UI says "Invitation sent." under the email (see image below)
6. Save event

Expected behaviour

An invitation received at the entered email address; expecting identical behaviour as when the vent is created to the calendar Personal.

(To be clear, the invite is sent when creating the event into the calendar Personal.)

Actual behaviour

No email is received by the invited email address

Calendar app

calendar version: 2.3.1

Client configuration

Browser: Firefox 91.0.2

Operating system: Manjaro Linux

Server configuration

Nextcloud Version: 21.0.3

Updated from an older installed version or fresh install: Autoupdated by Snap

[ChristophWurst]

Duplicate of nextcloud/server#26668