Having knocked myself out trying to get my DE download to work, so I can read my paid-for book, I had a look at the source code for the download page. It is a loop. Right-click on the 'download now' button, look at the properties, and you will see that the URL is the same as the page you are already on. Not going to get very far with that.
Anyone having this problem: for the sake of all of us dumb useless users... contact the source of your eBook and ask for your money back, explaining why. It just MIGHT cause someone to repair the link.