Just tested this on Plasma 6.5 Beta 2, and it doesn’t work here either. I could create the account, but when I access gdrive:/ in Dolphin it says “Access denied to .” I selected access to Contact and calendar systems. So an upgrade of Plasma probably won’t fix it for you.
Didn’t even realize Plasma had this feature and I reckon support for it is bad because many here try to get away from Big Tech overall and moving to FOSS alternatives like Nextcloud etc.
One alternative to KIO probably would be to use contacts and such via Thunderbird (I used this for years).
Having said that, there might be something wrong with my KDE PIM installation, maybe that’s why. What do you want to achieve with this? Is it just about access to Gdrive?
I abandoned the whole KDE path when I discovered something called ExpanDrive. It just works - well, still having issues with one of my gmail accounts. But Gnome just failed, so, no time to cry