Appointments+ plugin confirmation emails not being received

We had appointments setup and working with google calendar to take appointments for leaving and waiting for car maintenance on this site. When the google API update occurred we allowed access with the same google calendar and it is currently taking appointments, syncing them with the google calendar, and displaying them on that calendar under the designated "Service Provider" (Leave Car and Waiting).

However, no confirmation emails are being received by the user (when they make an appointment) or by the wordpress admin email address or the service provider email addresses.

The Appointments plugin log shows the confirmation emails as being sent, but they haven't shown up in spam or otherwise from any of the appointments made since the API update or from any recent tests.

I've left my most recent test appointment active for reference.

Support Access has been granted from the WPMU Dev Dashboard and I've left this information in the associated message field.

Any light that you could shed on the lack of confirmation emails, is greatly appreciated.

Thank you!