C.A.T.S.: Crash Arena Turbo Stars is currently available for iOS v.8.0+ and Android 5.0+. A stable internet connection is required in order to play the game.
Make sure that you are connected to a stable Wi-Fi network. Keep in mind that if you are connected via mobile data (3G/4G) and the connection bars are full, this does not always guarantee a solid internet connection. Networks can sometimes slow down or get overloaded, especially if you are playing in a moving vehicle or if the network base station is too far from your location.