Kontact problem after upgrade

I recently upgraded from 12.3 to 13.1 on a KDE desktop, preserving my /home folders.

I now can’t get Kontact to work properly.

I use akunambol to sync the calendar & tasks with onemediahub (funambol), and the tasks and events are syncing (visible using the panel widgets) but are not showing in Kontact.

Both KDE PIM & akunambol believe there is only one calendar on the system.