Have you just download the .ACSM file and open it immediately? This message should happen if the .ACSM file is expired. For some security reason, the .ACSM file has an expiration time before its first fulfillment (download book with it). If you leave this file for couple of minutes, it may be expired and have to be re-issued.
ACSM file is NOT a book, it's a ticket to Content Server saying which book should be downloaded. When open this file with ADE, ADE will communicate with Content Server and download the books for you.
Does this work with you?