I need more details than that if you need help. What platform (Mac, Windows, Linux...)? If Windows, what version of Windows? (Windows 7 is not compatible anymore), Do you have any overlay app preventing the game from launching (Assuming it doesn't open at all)? If it starts and closes, attach the generated log (Location depends on the platform you're playing).
Then there are the usual common questions, Minimum requirements met, Video Drivers updated, etc.