Error! Check activation

I bought an eBook and tried to read it in Adobe Digital Editions but couldn't - I received the above error message.

I have 8 books bought from the same seller and can read 1 in Adobe Digital Editions - every other book gives the same error message.

I have deleted the progarmme, removed Digital Editions from the registry and Adept, restarted, logged into my Adobe account with my Adobe I.D, - installed Digital Editions - same result.

I can read the books in the library, but that's not what I got them for - I want to read them offline on my laptop.

Can anybody please put me on the right path?

Thank you so much.