Make sure you downloaded the correct file for the device that you are on, may it be Windows or Mac.
If you are certain you downloaded the correct file try deleting the game and re-installing. If this does not work try restarting your computer.
If that does not work I am not 100% sure what the issue may be, but be sure to get back to me if any of the solutions I have provided work for you. :)
-Tuxx