Calendar does not sync with thunderbird or android

Server
1

Steps to reproduce

  1. add appointment
  2. install tbsync in thunderbird and enter owncloud caldav link

Expected behaviour

appointment from owncloud is shown in thunderbird

Actual behaviour

no sync

Server configuration

Ubuntu 18.04 ownCloud 10.5.0.10

Web server:
Apache

Database:
mariadb

PHP version:
php 7.3

ownCloud version: (see ownCloud admin page)
10.5.0.10

Updated from an older ownCloud or fresh install:
updated

List of activated apps:
Enabled:

  • audioplayer: 2.8.4
  • bookmarks: 0.10.6
  • brute_force_protection: 1.1.0
  • calendar: 1.6.4
  • camerarawpreviews: 0.7.8
  • carnet: 0.19.1
  • comments: 0.3.0
  • configreport: 0.2.0
  • contacts: 1.5.5
  • dav: 0.6.0
  • diagnostics: 0.1.4
  • extract: 1.2.4
  • federatedfilesharing: 0.5.0
  • federation: 0.1.0
  • files: 1.5.2
  • files_clipboard: 1.0.2
  • files_external: 0.7.1
  • files_external_ftp: 0.2.1
  • files_mediaviewer: 1.0.3
  • files_pdfviewer: 0.11.2
  • files_sharing: 0.13.0
  • files_texteditor: 2.3.0
  • files_textviewer: 1.0.3
  • files_trashbin: 0.9.1
  • files_versions: 1.3.0
  • firstrunwizard: 1.2.0
  • gallery: 16.1.1
  • impersonate: 0.5.0
  • market: 0.6.0
  • metadata: 0.10.0
  • notifications: 0.5.2
  • oauth2: 0.4.4
  • provisioning_api: 0.5.0
  • systemtags: 0.3.0
  • tasks: 0.9.7
  • updatenotification: 0.2.1