This problem often shows up in Internet Explorer and sometimes in Safari. Please try using the latest version of Google Chrome or Firefox.
Make sure to check that your internet connection is stable and can handle the resolution that the video is playing at (e.g. 720p or 480p).
If none of these work, please try restarting your computer before contacting us.
Our video lectures are hosted by Vimeo. Please go to Vimeo.com to try to play a video. If your video won’t display, your firewall or anti-virus software may be blocking access. Whitelist the domains below in order to access Vimeo videos: