I just noticed that of the “my calendars” that I have in Google, the only one that I cannot create a new event on from HA is my primary account.
So, HA is seeing the calendar, but it’s not able to access the calendar. This calendar is the primary calendar for a Google Workplace account if that makes any difference.
And it’s because, as I’ve discovered, that I had manually configured my calendar in a file called “google_calendars.yaml” to limit the sensor to only seeing events that had a specific search term in them.