The vendor account you entered is not associated with the item you are trying to open

I'm trying to access my e-books that I bought on Adlibris.com. However, I can only open a few of them. The following error message is displayed when I am trying to open new e-books "The vendor account you entered is not associated with the item you are trying to open". Although, the Adobe ID is correct.

Why can't I open all my e-books on Adobe Digital Editions? I use version 4.5.