Cannot connect to EndNote Web from EndNote X2.0.1 (Mac)

I cannot connect to my EndNote web account from EndNote. I have checked the email address and password and can log in fine from a browser window. I’ve deleted EndNote and its support files and reinstalled, with no difference. The subwindow “Authorizing” pops up and runs and runs, with no action. Does anyone have an idea of what might be amiss? 

If I go to Preferences, delete the fields that I filled in and try to register for EndNote Web, I get the message “EndNote Web registration could not be completed. The serial number you entered is invalid.”. 

Thank you for any ideas.