Type up a letter detailing ticket#(s), flights, fare classes etc, and send along with copies of boarding passes via mail and fax. Wait for response from DL, and repeat as needed. Keep doing this until someone who receives it puts the miles in your account.

In my experience CI is the most difficult carrier to get skymiles with, not sure why this is. I have had to send and re-send and re-send in the past to get what I am due. This even happened to me for the DL codeshare CI flight to LAX, booked on DL.com!