Use the URL you suggest, https://apidata.googleusercontent.com/caldav/v2/yourID/events, but rather than using email@example.com as the substitute for yourID, put in the calendar name instead.
To find that name, start with a Google Calendar window, then go to Settings->Calendars and click on the name of the Calendar you care about. Now scroll down ...
I suggest the following procedure to find out the CalDAV and CardDAV connections files:
Take a copy of the ~/.thunderbird folder
Add or drop one such connection
Check which files have changed
Compare the changed files using diff
if they are textual in nature and if you would like to ensure you are copying the
(or if you are curious about the ...
I found a solution to this problem, which I also had on Ubuntu 19.04.
Thunderbird 60.8.0 (64-bit)
What I did:
deactivate the affected CalDav calendar in the list of (using properties/ uncheck "Switch this calendar on")
remove the password authentication entry in the preferences/preferences/security/saved passwords menu
Try this: https://syncthing.net/
It is peer to peer. So when the client is online (network) syncthing, what is running in the background sync the files. It is working with macOS, Windows and Linux.
Sync the hole thunderbird folder. After the first sync it syncs only the files hat have changed.
Disclaimer: I don't know anything about CalDAV and CardDAV and how Thunderbird handles them. However, I hope I can give some general guidelines.
Comparing directory trees and files in Linux using a graphical UI
Some of the other answers / comments have proposed to take a backup of your profile, delete one of the CalDAV / CardDAV connections, and check what ...