Bookings Page not sending confirmation emails to customers

The problem appears to stem from the way Microsoft Bookings manages its underlying mailbox. Each Bookings calendar is associated with a hidden Exchange Online mailbox, typically identified by a randomly generated string address. This mailbox is responsible for sending confirmation and reminder emails. If the mailbox has not been correctly provisioned or licensed, confirmation emails will not be delivered to customers even when the “Send confirmation email” option is enabled.

https://learn.microsoft.com/en-us/exchange/recipients-in-exchange-online/manage-resource-mailboxes

https://learn.microsoft.com/en-us/answers/questions/5305069/microsoft-bookings-problems

https://learn.microsoft.com/en-us/answers/questions/2284702/not-receiving-confirmation-email