Most likely, your internet connection is faulty. Make sure everything is ok with it.
Make sure you have latest Adobe Flash Player installed, and if required, please install it.
After you’ve performed the verification of internet connection and Adobe flash player, clean up the internet cash (for most of the browsers the combinations CTRL+R works), game must work fine, If game is not running, and you see the black screen, please try another game. If nothing helps, please contact customer support and report the issue.