When users open a meeting request they created and see the error message "Invitations have not been sent for this meeting" even though the meeting request was sent (and responses received from the recipients), they are often confused because the message was sent.
Additionally, they may receive a message when they close the meeting invitation: "
Although the displayed message gives the impression that the meeting request has not been sent, you do not need to send it again. The attendees who received the meeting request when it was originally sent will not be affected.
This is the result of exporting or moving the meeting to a Calendar in a pst file (or moving the items back to the Exchange calendar). Although it happens less frequently, it can also occur when a pst file is set as the default message store for an Exchange mailbox.
When you move or export the meeting events to a pst file, the meeting request status and attendee response status are not exported. As a result, when the meeting or invited event is opened, the Info bar will display "Invitations have not been sent for this meeting" and will ask if you want to send it when you close the meeting.