There could be many reasons for the lab environment not loading. 
 
Here are some possible causes;
  • security software on the computer you are using. The lab environment utilizes web sockets, which some security software interferes with.
  • security mechanism on your network. If you attempting at your work place, and you work in a secure environment, the web socket connection from the source back to your computer may be blocked.
  • "Advanced Security" provided by some home Internet service providers also causes a problem, for the same reason
  • Asymmetric routing, which would really only happen if you are attempting to access at work, and your organizations external return routes are not the same as outbound routes.
If you are attempting to start the labs at work, try at home and perhaps with another computer.