[kronolith] CalDav problems with 2Do-App

[Trepper Thomas]

Hi all, 
 
I have issues setting up the 2-Do app (http://www.2doapp.com/) <http://www.2doapp.com/)> and making it sync via horde. I use horde groupware 5.2.2 installed via the official Debian Jessy repositories. I went into horde copied out the link to subscribe to a calendar and used this one but on syncing it always gives me a 403 but the same credentials are working in mac calendar.
 
I am trying to find out where the issue is and just wanted to ask if someone else in this community is using this app as well together with the CalDav sync?
 
Any help highly appreciated. Thank you very much in advance and all the best,
 
Thomas