cannot add calDAV/cardDAV account - 'an unknown error occurred'

I am trying to setup OS X Server to backup contacts and calendar - no longer easily possible in Mavericks without icloud, which i do not want to use.

I follow the instructions from Apple, here [http://krypted.com/tag/setup-caldav-client-for-ical-server/] and one or two others, which agree with each other.

I am running Mavericks, everything updated, now the second OS X Server installation.

Now i cannot add accounts, either from within the app or in Sys Prefs/Internet Accounts. I click 'Add Other...' , choose Add CalDAV, there i choose Account type: Manual, and enter the username [without any @, i.e., not an email address], the correct password and then the server address, which ends in .local.

There is a while of Verifying... Then the usual 'Server with secure communication unavailable' warning, where i click Continue.

Then i am right back to the 'Add a CalDAV account' screen, with the added comment at the bottom, 'An unknown error occurred.'

If i leave off .local for the server address, verifying is quick, but the results are the same.

If i enter information i know is wrong, the result is the same, which makes me think i am entering something incorrectly. But i have checked: in Server i have made this user account, i know the name and password well. The user is given access [only] to Calendar and Contacts. Those services are turned on, as is Server itself.

Then in Calendar i try to add an account, or in Sys Prefs, same results.

Have been searching a lot for any reference to this, but i seem to be one of the few.

What the **** am i doing wrong? Please give any references i could learn from and solve this problem.

Thanks!