SharePoint Document Relationship missing

Hi,

I have integrated SharePoint with CRM 2015 onpremise. And I've linked document entity to upload documents and store in Sharepoint.

But the relationship called 'SharePoint Document' for document entity is not showing up in the 1:N relationships of document.

What am I missing? I do able to navigate to the document upload iframe through navigation bar.

Please guide me through this.

Thank you.