Invitation email with iCal file from NC32 not fully recognized in NC33

Steps to reproduce

1. Open Calendar in NC 32, create an event and invite an attendee email that has their email and calendar set up in NC 33.
2. In NC Mail in NC 33, see that the invitation email is recognized and the buttons "accept, decline ..." are displayed.
3. However, in the Calendar in NC 33 the event is not displayed as pending and there is no notification about the invitation. Also, in a connected calDAV client like Apple Calendar the invitation is not presented.

Calendar Versions:
NC 32: 6.4.1
NC 33: 6.4.1

Expected behavior

The invitation should be presented in NC Calendar, the notifications and calDAV clients.

Actual behavior

The invitation is only presented in Nextcloud Mail.

Calendar app version

6.4.1

CalDAV-clients used

No response

Browser

No response

Client operating system

No response

Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

No response

Updated from an older installed version or fresh install

None

List of activated apps

Nextcloud configuration

Web server error log

Log file

Browser log

Additional info

No response

Start by reproducing the NC32-to-NC33 invitation flow in NC Mail and Calendar, then inspect how the invitation reaches the CalDAV client. Done means the invitation appears as pending in NC Calendar, generates its notification, and is presented by a connected CalDAV client.