“Calendar usage limits exceeded” when adding event with attendee

When trying to use the Create Event to ‘create’ new events with external attendees, I hit some kind of quota limit. But it works fine when the attendees is empty. Can anyone have any idea? :roll_eyes:
I am pretty sure that it is not regarding to the quota or that kind of limitation stuff.
Any help would be highly appreciated.

The error I got is
Message: Google.Apis.Requests.RequestError
Calendar usage limits exceeded. [403]
Errors [
Message[Calendar usage limits exceeded.] Location[ - ] Reason[quotaExceeded] Domain[usageLimits]

Exception Type: Google.GoogleApiException