how to generate a report indicating viewed not completed

Choose the Envelope report under (https://support.docusign.com/guides/ndse-user-guide-using-reports) the Reports tab .

Edit your filter to show Status as either "Sent" or "Delivered".

Delivered means the current recipient got the email and actually opened and viewed the documents.

Sent means the current recipient only received the email but haven't opened it yet.

So if an envelope has multiple recipients it could bounce between Sent and Delivered until finally Completed.

Hope this helps