I'm trying to sync KOrganizer Calendar with Zoho Calendar through Caldav

Events from the Zoho Calendar don't sync to the KOrganizer Calendar and vice versa

In Settings > Configure KOrganizer > Calendars Tab
I see that the CalDav Calendar account is stuck at "Fetching collections (0%)", even after multiple computer reboots.

I don't know what log file to pull to see where the sync process is hanging

I'm using Kubuntu 20.04. I've install the entire Kontact suite with:
$ sudo apt install kontact

KDE Plasma version: 5.18.4
KDE Frameworks version: 5.68.0
Qt version: 5.12.8
Kernel version: 5.4.0-29-generic
OS Type: 64-bit
Processor: Intel Core i3 6300