Not able to Sign-in to WPMU through website

After install/activating the WPMU plugin, I go to sign-in to my WPMU account from the website. But after I enter my login information and hit submit, the screen just sits there with the loading icon spinning (screenshot attached). However, I believe it has something to do with the website server, possible blocking external connections. I think this is the case because, I am not able to see any external feeds being pulled in on the Dashboard (i.e. WordPress News, just says loading ) see screenshot attached.

Any help identifying the problem, will be greatly appreciated!