OCLC status us still "RECEIVED - OVERDUE". When you try to complete the request manually, you get an error message that says "Error updating the OCLC Item Request (Exception of the type 'AtlasSystems.Oclc.ResourceSharing.ValidationException' was thrown.)."
The borrower needs to mark it as returned. Then, you can check it back in.
You could also try going to the OCLC Request tab at the top and "Recall" the item if it is available. Once you recall it, you might be able to check it in. If you are not, you need to contact the borrower and have them mark it as returned.