O365 Groups, Shared mailbox and public folders not working

Oliver Blanchard 0 Reputation points

I Have a site that currently has an issue where they cant access Shared mailboxes or 365 Groups.

The shared mailboxes will not appear in the users mailbox after they have been given the correct permissions.

You can manually add these mailboxes to the users mailbox in there session but then if you try and open the mail box you get a message stating, 'The set of files couldn't be reached' or 'The profile is currently in use (.ost file currently in use)'.

I also have a Microsoft 365 group which holds there team calendar, this was previously a public folder when they had a on premise Exchange.

Again i will assign the permissions but it will not appear in anyone's Outlook, then you can manually join the group but it will not show anything and after you close and re-open outlook the group will have gone again.

The Funky part is that any user created after there O365 migration is not affected by this and can open shared mailboxes and groups without issue.

Any help would be greatly appreciated, if there's is any extra information needed please ask.

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Formerly Office 365, is a line of subscription services offered by Microsoft which adds to and includes the Microsoft Office product line.
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A Microsoft app that connects remotely to computers and to virtual apps and desktops.
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  1. Shaofan Lv-MSFT 3,320 Reputation points Microsoft Vendor

    Hi @Oliver Blanchard
    Do you mean "The file C:\users\….username.ost is in use and cannot be accessed."?

    From what I've found, restarting your PC might help. So, is the problem still there? If we misunderstood something, could you provide some screenshots?

    Also, you could share with us that you have tried so far.



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