Can't authorize computer

I just installed ADE and tried to open a book. ADE gave me the option of authorizing the computer. The book is from OverDrive via the local library.  I selected Overdrive from the drop down menu, entered my login information & ADE was unable to  authorize.I double checked to make sure it was correct by logging directly to OverDrive & it worked fine. I tried to go back & try again, but "Authorize Computer" is greyed out...