We have been happily using a custom function in Zoho Books for over a year to create Zoho Calendar events for our field technicians.  The custom function creates the event at the proper date and time, adds the necessary technicians, and creates the event in a shared calendar called "Service" with me as the organizer.

In the past several weeks we have missed service calls due to these events not showing up in our calendars, and we are receiving customer complaints that severely impact our online reputation.

Most notably, when I run the custom function to create the event, I am listed properly as the organizer but I no longer receive the invitation as I used to, and the event does NOT appear in my calendar!  When our receptionist runs the custom function, I will receive an invitation most of the time, but NOT always!

Why is there a change in behavior in the calendar app, such that events I create appear in the Service calendar, but not in mine?  Is there an obscure setting somewhere?  Has the API changed?