Your server sends an invalid redirect:
Considering that my setup was normally working, upgrading to 9.0.2 resolved the issue which was due to upgrade to PHP-7.0.6 - see this link.
Thank you for your response.
Right now we require to setup two accounts if we want to sync carddav and caldav from an owncloud server. It would be much more user-friendly if both would work with an owncloud server. It actually works confusing, when davdroid says ‘select contacts to sync’ and there is nothing there. I actually searched in my owncloud setup first.
This is not related to DAVdroid but to Owncloud. DAVdroid uses WebDav Current Principal to auto-detect collections. Some people say that they only need to enter a single URL/account for OC6, I have never seen that.
Please refer to the OwnCloud support for that.
For reference, here’s the owncloud ticket that goes about it.
Should get merged with owncloud 7