That means either (1) The sender failed to click "Cancel" on the request or (2) The sender had marked "mailed" already and there is no "cancel" button for him or her to click or (3) The sender (or the system) canceled, and a NEW sender is sending the book to you.

If the situation is (1):  the sender needs to click Cancel Order on the request. 

If the situation is (2): the sender needs to contact us to cancel this.

If the situation is (3): you will get the book from this new sender.  Nothing more needs to be done.

Notes

• How to tell if the situation is (1) or (2) or (3):

  • Click the PM button on the active request on your My Account page
    • If the name in the TO field of the new PM is the same as the name of the sender who told you s/he canceled/cannot mail, then the situation is (1) or (2).  Then look at the request. If it is on the Books i've Requested tab and has not been marked mailed, the situation is (1).  if it is on your En Route to Me tab, it has been marked mailed and the situation is (2).
    • If the name in the TO field of the new PM is NOT the same as the name of the sender who told you s/he canceled/cannot mail, then the situation is (3).  You will get the book from the new sender. 

• If the situation is (1) or (2) you should send a Personal Message to the sender asking him or her to cancel  (or to contact us to cancel).   Give him or her two or three days to read your PM and do this, and if it is not done by then, contact us from the feedback link at the top of the Contact Us page and we will cancel and educate the sender.

• If a sender says he or she clicked Cancel by mistake or that the system canceled the request:

  That means the system would have passed your request to a new sender if it was possible (if there was another copy of the book in the system when this canceled).  So....

  • if the sender HAS NOT MAILED the book:
  • Tell that sender NOT to mail.
  • Tell that sender to repost the book, for the reasons explained in I canceled a book request by mistake! and My request was canceled--I didn't mail the book yet.
  •  
  • if the sender HAS MAILED the book:
    • Look at your My Account page. If there is an active request there, with a new sender, then that means you will end up with 2 copies of the book.
    • Click "Cancel Order" on the new request if there is a Cancel Order button
      • If you are able to cancel, then you will get only ONE copy (the first sender's canceled copy) and you can mark it received from your Transaction Archive when it arrives, as described in I received a book from a canceled transaction!.
      • If you are NOT able to cancel, then you will get 2 copies and you will be obligated to mark only the second (properly-sent) copy received, as described in I received 2 copies of the same book!.  You are not obligated to give a second credit for a second copy of a book if you submitted only one request. You are not obligated to return the extra copy

Related Links:

How do I cancel a request?
My request was canceled --but I mailed the book!
How can I tell who's sending me a book? (or to whom I am sending a book?)