Usually, one of the following steps helps to resolve any issues that occur when trying to start a game.
Please try them if you haven't done so:
1. Update your browser to the latest version
2. Clear old cache and cookies
3. Try a different browser (Chrome, Firefox, Internet Explorer)
If you have tried them all but still can't open the game, please kindly send us an email with the game name and the screen capture of the error message you keep getting.