[horde] Problems connecting Horde to Mac Contacts via CardDAV

[Thomas Trepper]

Hi all, 

I am running Horde 5.2.19 and want to connect the included addressbook from apple (Mac OS Sierra 10.12.4) (contacts.app) with Horde. 

I have a list in Horde called „private", I clicked on edit and copied out the first (and tried the second link as well). I copied the links into the contacts app into the CardDAV account and server information. The check for valid username/password works, the account is added to the list in the native app, BUT it does not load any contacts. 

I have checked logs but I do not have any ideas where to start searching? Does anyone have any ideas to point me into the right direction please?

Thanks a lot in advance and all the best,
Thomas