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 to uninstall and reinstall the game from the Play Store:
- Launch the Google Play Store app from your home screen or app drawer.
- Tap the search bar at the top of the screen.
- Type Football Manager Mobile 2018.
- Tap on the installed app.
- Tap Uninstall.
- Tap OK to confirm uninstall.
- From the Google Play Store app.
- Tap Menu followed by My Apps and games followed by Library.
- Tap the app you want to install.
- Tap Install.
If you are still receiving this message after trying the above, please mail firstname.lastname@example.org where the team will be able to get things working for you.