Collabora Online under owncloud

[Killerkirsche]

I think, my problem is simple... I just installed owncloud and then collabory online. A corresponding context-menu appears for office-documents, but when I press it, the following error message rises:
Collabora Online: Ungültige URL "".
Bitte kontaktiere deinen Administrator. Er kann die Collabora Online Einstellungen überprüfen und dir helfen.
I am administrator...
What kind of preferences I have to make ?
Kind regards
Killerkirsche

[jnweiger]

Please study the setup instructions at
https://doc.owncloud.com/server/10.12/admin_manual/configuration/server/occ_command.html#collabora-online-secure-view

When it says "Ungültige URL", it probably has an empty 'wopi_url'

The URL can be set via occ command line or from the admin -> Settings -> Additional