Create bookingStaffMember also requires Add-MailboxPermission

You’re right that adding someone as a staff member through Graph doesn’t automatically give them access to the scheduling mailbox, which is why they still see the “no access” message. Granting Full Access with Add-MailboxPermission definitely solves it, though in many cases giving them Calendar folder permissions is enough if you want to keep access more limited. As long as the user has the right license and you allow a little time for permissions to sync, they’ll be able to open and manage the Bookings page. Your method works well, and using folder-level permissions is just a lighter alternative if you prefer a least-privilege approach.

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