I'm using a Jolla Classic, with latest official updates and got a bit of syncronisation trouble.
The reason for my troubles is that my ownCloud provider just became my NextCloud provider, the switch has brought on a bit of syncronisation troubles.
Deleting and recreating my syncronisation connections fixed the calendar/CalDAV problems, but I still got Contacts/CardDAV problems.
It seems the Jolla is unable to sync the existing contacts stored on it. If I create a new one, on the Jolla, it gets synced correctly. If I create a new one on the server or KAddress it also gets syncronised correctly to the Jolla.
Is there a way to force a sync of my Contacts?
Well I decided to manually duplicate all contacts entry.
By adding the number 2 to all lastnames and copy the information, one string at the time and forcing a synchronization between each - otherwise it refuses to syncronise.
At the moment, it seems, that I am unable to synchronize the pictures - but that is only a nice-to-have.
I wonder it there is a difference in the implementation of CardDAV in ownCloud and nextCloud?
The ownNotes app seems to work just as well on nextCloud BTW - good job dude! (I just wish that I had just as good a program om the KDE side of things.)