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The set of folders cannot be opened

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Hello there, I've got a huge issue going on with my company. We have a main account on our Exchange that shares its three calendars (General, Seminars, and Surgeries) with all the other users in the company. Two days ago, my employees started saying that they were receiving a "The set of folders cannot be opened error," and now, all calendars besides the main calendar have gone missing from the main account, both on Outlook and online.


Are there any backups stores of our calendars? How can we access these? We are devastated to have this information lost, and our employees would not have deleted the calendar. 


Please help, this is driving my business to a halt as we do not know when any of our appointments are.


Thank you,


All Replies
  • Hi Sam,

    From the information you post on the forum, I understand that two calendars are missing from both Outlook and OWA.

    To help resolve this issue, could you provide the following information for us to troubleshoot?

    1.What did the users do when he encountered the error message “The set of folders cannot be opened error”?
    2.Please post a screen shoot about the whole content of error message here for us to troubleshoot.
    3.How did you share the calendar? Did you share the calendar by right click the calendar->share or by PowerShell or publishing the calendar?
    4.What the permission the users have for the shared calendar?

    Additionally, please refer to the steps below to check the service health for the main Exchange account:

    1.Login MOP at ( as global administrator.
    2.Click Service Health under Support in the left navigation.
    3.Check statements of Exchange Online section.

    Please refer to the link below to get more information about the service health:
    Office 365 for enterprise:
    Office 365 for small business:

    Linda Wang

  • Hi Sam,

    Just checking in to see if you have any other related questions.

    If so, please do not hesitate to contact us. It is always our pleasure to be of assistance.

    Linda Wang