Hi there,
i just upgraded to 9.0 because my cardDAV connection to BusyContacs is not working anymore.
I switched to busyContacts because the default Contacts App on macOS El Capitan and Sierra are not working with my owncloud installation either.
Do you guys have a tip how to fix my cardDAV installation?
Can you give more details about your problem? Error message, logfiles, ...
actually the only thing that BusyContacs shows is "not able to connect to server".
Without any errors its unfortunately not possible to help here. Maybe try to contact the author of this app to get some support for this issue from him.