Can't download my ebook to ADE, why?

Hello mates,

I've purchased an ebook and when I tried to download it to ADE I got a message saying "Error getting License. License server communication problem: E_ADEPT_NO_TOKEN"

What does this mean? I feel like I've tried everything to make it work but it doesn't. And sense I have as much knowledge of these kinds of programs as my grandma, I kind of need some help!

Thanks,

Johanna