When editing/rescheduling an existing meeting for another staff member, an error says “The operation failed”

This problem affects delegates trying to edit meetings created prior to migration on behalf of another staff member.

If you find you are unable to edit or cancel the invitations created prior to your migration, you will need to ask each invitee to manually delete the meeting (and any subsequent meetings) from their own calendars.

After the invitees have been notified, a new meeting invitation can be created.