Microsoft Bookings allowing appointments when staff Outlook calendar is Busy

Dear Ifeoma,

Unfortunately, as a forum moderator, I am not able to inspect your Bookings calendar or Exchange configuration to diagnose this directly. My role here is limited to general guidance you can apply from your side.

The fact that Scheduling Assistant shows the staff correctly, while Bookings does not, is a useful clue. It suggests the mailbox data is fine and the problem is in how Bookings is reading, or not reading, that availability. The first thing I would check is how the affected staff were added to the booking calendar. Bookings only checks Exchange availability for staff added with a work account in your organization. It would also help to know a few things:

• Does this affect every staff member, or only certain ones?
• On the affected service, is "Maximum attendees per event" set higher than 1? If so, Bookings will intentionally allow multiple bookings in the same slot.
• Are the conflicting events on the staff member's primary calendar, or a shared or secondary one? Bookings only reads the primary calendar.
• Are your mailboxes fully in Exchange Online, or is the organization hybrid?

That last one matters because Bookings reads availability from Exchange Online, whereas Outlook's Scheduling Assistant can surface hybrid free/busy information. If any affected mailbox is still hosted on-premises, that difference could explain the mismatch, though I would treat this as a secondary possibility behind the staff membership type.

I hope this helps. Once I know how the staff were added and whether the service allows multiple attendees, I should be able to narrow this down further. Looking forward to your reply.

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