Digital Editions not letting me authorize

Please help. I bought textbook of the site eCampus, and tried to get Digital Editions to let me authroize my computer to get my textbook. I have been unable to authorize my textbook. I have re-downloaded the program twice, once as the 3.0 version, and no luck. To make matters worse I can not access my acount that I made when I bought the textbook. I'm so frusrated and feel ripped off.