Thanks for the quick reply and for a great plugin!
Looked at the debug.log and there are probably things that can be improved but it’s no longer important that the administrator can delete bookings in the calendar as long as notifications are sent to both customers and administrators. That was the main issue.
I checked the calendar settings one more time and these settings worked for me:
– Display format of the “Arrival and Departure” – Arrival (Check-in) & Departure (Check-out)
– Notification – Canceled (Email and HTML)