Since Re-activation as suggested by the link above is not working for you, Can you please confirm the following:
The OperatorURL is reachable. ( you can find the operatorURL from the acsm file by opening it in notepad,etc)
And Book is still available on the book-store for purchase.
(If any of first two are not available, you might have to talk to distributor for next action item to get the book. Since you will have record of purchasing the book, (in my opinion) they should provide you the new token for downloading the book)
And please confirm this that you used the same userID for downloading that you used when you first fulfilled/downloaded the book.
(If it is the case, then you have to use the correct userID)
I hope it helps.