ADE Connection error detected

I am attempting to use Adobe Digital Editions and have downloaded an ebook (in the supported format); however on trying to open the book, I get the error message "Connection error detected.  Digital Editions could not connect to the fulfillment server. Please make sure you are connected to the internet." I am connected to the Internet. I have tried deauthorising and reauthorising ADE to no avail. It would be helpful if someone from Adobe answered this question as I can see the question has been posed many time but remains unanswered.