OSX CardDav sync not possible

Although the CalDav sync functions properly, I CANNOT get CardDav working on my MacBook Pro running 10.11. So, the suggestions to modify .htaccess seem to be redundant. I wonder if my issue is within the Apple’s configuration/cache etc.

This is becoming quite frustrating, particularly since in addition to being able to synchronise my calendar activities on my Macbook without fail, I have no issues to synchronise both calendar and contact entries on my android devices.

Surely there must be others facing the same issues. Any suggestions, please?

*currently running Nextcloud 12.0.0

A few minutes ago I deleted the carddav account and the AddressBook.plist file and then rebooted my MBP. I restarted the box, opened Contacts and added a new CardDav account using my Nextcloud settings. Shortly afterwards, a new address book was created and populated with the contacts from Nextcloud. Great! But…

After adding a new contact in the cloud address book on the MBP, Contacts tried to synchronise back to Nextcloud. This was unsuccessful. The resultant error message was:

The operation couldn’t be completed. (CoreDAVHTTPStatusErrorDomain error 500

This is driving me nuts…

Although the address book on Nextcloud is called, for example, “BAR” I just noticed that the address book which was imported into my MBP is called “FOO”. Strange since there is currently no address book with this name on the Nextcloud server.

“FOO” is the name of an earlier Nextcloud address book which I had deleted. It was recently replaced on Nextcloud by “BAR”

Seems to be a cache issue somewhere. Any idea which files I must trash?