There are several cases where when I connect with my admin account to browse the Office 365 Resource Calendar, the attendance buttons are missing from time to time, and I have no clue why. These meetings are still valid and existing meetings in the organizer inbox, but from the Resource Calendar, the only option is "Delete".

See normal Resource Calendar meeting attendance option

vs. the missing attendance option and only the Delete option available

Anyone have seen same behavior and knows why it is happening ? Thanks!


At first, I suspect that this issue is caused by the room mailbox didn’t accept the meeting request, but based on my test, this is not the root cause.

Did you test on OWA? This can rule out the Outlook client issue. Did other room mailboxes have the same issue? You also can compare its settings with the working one.

  • Yes it is happening on OWA. The room mailbox did accept the meeting all the time, that's why I don't get why the attendance options are gone. The meeting is also present in the user's calendar, with the room status as accepted. Some other room mailboxes also show this behavior from time to time, really scratching my head to understand why he would do that for some valid meetings, really seems to happen randomly... – spmsh Sep 23 '20 at 1:31
  • It is hard to troubleshoot the random issue. When did this issue happen, did you do any modifications? You could create a new room mailbox for test. If the issue persist, you may need to contact O365 backend support via SR. – Jayce Yang Sep 23 '20 at 9:30

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