I have a peculiar problem.
When I add a new entry to Google Calendar in a browser or in my Android cellphone, it quickly updates KOrganizer running in KDE Neon,
In contrast, new entries to KOrganizer on my desktop machine do not show in Google calendar.

I tried reinstalling Kontact and Korganizer. I tried deleting and adding back the link for Google Calendar in KOrganizer.
I used Muon to add libraries for KOganizer that had any mention of calendar in them. (I was "inspired" by an entry here: https://bbs.archlinux.org/viewtopic.php?id=232823 )
Nothing worked to change the failure of KOrganizer entries to register in Google Calendar.

A workaround is to make all new entries through Google Calendar either in my Firefox browser or in Google Calendar on my Android cellphone.
I don't like that as I want KOrganizer and eventually Kontact to be primary.

In one place I looked someone mentioned using KWallet was important. I've not used KWallet and don't know why I should, but if it is important I will adopt it's use.

Previously, I had a different issue when I mistakenly disabled KOrganizer on the same machine entirely.

At that time I was able to rebuild KOrganizer on my desktop by copying entries from KOrganizer on my laptop, an Asus Transformer 3 Pro. Unfortunately, the Asus T3P is in the shop with a swollen battery as I await word whether that issue and other aspects can be repaired. KOrganizer on the T3P synced both directions, if I recall correctly.