Hi,
First make sure you've copied the .pst file to your local drive, not on a network share which is not supported.
Then, start Outlook with "Run as administrator" option from the right-click context menu, then try to attach the .pst file again, see if that works.
If issue persists, check the properies of this .pst file, make sure the file is not Read Only. To do this, right-click the file, click
Properties, click to clear the Read Only check box, and then click
OK.
Hope this helps.
Regards,
Ethan Hua
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact
tnmff@microsoft.com