Firstly, please ensure that the device's memory card is not mounted as an external drive on the computer. Mounting your device as an external disk will leave the game (and probably most of your other apps) unable to run.
Secondly, please try fully rebooting your device and running the game again. If neither of the above have met with any success, it's possible that some of the game's data may be corrupt - this is especially likely if you have only just installed the game and have never been able to get it to run. If this is the case, please try uninstalling the game, then restarting the device and re-installing the game from the Play Store.
If the game is still not working correctly for you, please create a new thread on our bugs forum: http://community.sigames.com/forumdisplay.php/530-Android-Bugs-Forum