I'm having the same problem. Just installed Adobe Digital Editions 4 on my Windows 8.1 computer and can't get to ADE's to download or return books to my library. The Overdrive app seems to be working fine but ADE's won't start? I don't get the open pop up. Books I have checked out of the library show in ADE's when I go to it independently. Sure hope someone has an answer.
i cant download also.
My error is "Error getting LIcence Licence communication problem E_IO_CANNOT_OPEN"
this is not a once off, the problem has been there for months
My solution on a MacBook Pro with El Capitan
1. Opened my hidden Library folder
a. Opened Finder
b. Pushed & Held “Option” key and clicked “Go” in the title bar (“Library” appeared)
c. Clicked “Library” while Holding “Option” key
2. Went to /Application Support/Adobe/Digital Editions
3. Deleted the “activation.dat file”
4. Deleted Adobe Digital Editions (I did it with Clean My Mac 3 but you probably won’t need to use it for the deletion)
5. Emptied Trash
6. Reinstalled Adobe Digital Editions 4.5
7. Adobe Digital Editions opened authorization popup, which I filled out
8. My files now open perfectly