Unable to add e-book and to remove authorization PC

Hi. I installed Adobe digital editions yesterday. After trying to import an e-book I got the error message "Error! Check activation." In forums I found that I need to remove the authorization for my PC (windows) and add it again, but I even get an error message while trying to do that: it mentions that I have to try it again later. I'm already trying 2 days, but still no change. How can I solve this?