I know many people have discussed this before and I have tried all their solutions (I think ).
Up till the 16/06.15 I had no problem borrowing books from my public library for at least a year. I can't think of anything which has changed apart from the date.
Today (20/06/15) I get the message, "Digital Editions could not connect to the activation server. Please make sure you are connected to the internet."
OK, I'm stuck for the next idea. I'm limited by the license terms about how inquisitive I can get, (and I can't justify the time.)
Bright ideas anybody? Everything worked fine until today.
I am also having this problem. Originally using 2.0, Windows 7 up until a little over a week ago when ADE said that it could no longer connect to the fulfillment server when I tried to return books so tried to deauthorize and reinstall, which yielded the Connection Error - Digital Editions... message. Authorizing with Windows firewalls completely down (exception didn't work) makes it go through to the authorizing step with the flashing green bar and the Please wait while your computer is being authorized, but it just keeps on flashing without ever going through. Tried 4.03 for an hour, uninstalled, restarted, tried with 2.0 and same thing.
The only thing that has changed recently in the computer environment is the installation of the Windows updates released this month.