If you have purchased the game from Google Play and you are receiving a message that the game is from an unofficial source, firstly try opening the Google Play app to check that there are no connectivity issues with this.
If this does not work, try rebooting your device, ensuring you are logged into the Google Play account used to purchase the game, and then try to run the game once again. You should only need to do this once. If this does not work, please try the following steps. We reco