Do you have a firewall on your computer? Turn it off for a while! It can block your access to some sites so that even if you are logging on to the site you can’t view anything there. Firewall can also prevent you from downloading some information you might need. So, a firewall should be disabled for some time. But you can re-enable it as soon as you complete the session.
Also you may install Adobe Flash Player. Download it, install and restart your computer after installation. Now it should stream the videos.