I am not able to open the book and getting error Digital Editions could not connect to the fulfillment server. Please make sure you are connected to the internet.
using Windows 8 computer.
I have installed ADE 2.0 on my Win 8 and it look fine. There should not be any problem. As far as you error is concerned, you might need to get in touch with the e-book provider.
Did you check, if you get this error only while opening a particular e-book or it happens with all of them?
Try opening some free e-books and check if that works fine.