Can't get shared calendar to save permission changes

I'm trying to edit the permissions on a shared calendar to give "delegate" permission to the calendar, and to remove an old entry from the list of users.  Neither change will save, I get an error that says "modified permissions could not be saved".  I tried sending an invite to the calendar and it switched permissions for that user to "custom" and they can view but still can't add or edit as "delegate" would, which is what we need.  On a brand new, blank calendar, there are no permission issues but it would not allow me to copy and paste all the entries from the old calendar into the new one (and this is not an ideal solution anyway, just a band-aid).  This is a hybrid environment w on-prem Exchange and Office 365 syncing.  It's very important we get this working asap and any help would be greatly appreciated.  Thanks in advance.


Hi Scott,


Based on my research, I suggest you try to grant, apply, and then remove Delegate access. This action forces a re-write of the Access Control Lists (ACL) at the mailbox level, which propagates to the folders.


  1. In Outlook > File > Account Settings > Delegate Access
  2. Click Add, and then click any user in the global address list field.
  3. In the Permissions page, click OK, click Apply, and then click OK again.
  4. Select the File tab, click Account Settings, click Delegate Access, and then remove the user that you added in step 2.


If the issue persists, I’d like to collect some detailed information as below for further investigation:

  1. How did you edit the shared calendar permission?
  2. What’s the version of your Outlook?
  3. A screenshot of the error message.




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Question Info

Last updated August 25, 2021 Views 11,785 Applies to: