If you invite your friends through Facebook, your friends need to click on the link you shared to download the game. This means that you can only invite friends who do not have the game or an account in it. If your friend was invited by three different people, the link he clicks to download the game will be the friend who gets the reward. The reward can only be claimed when your friend reaches level 3.
How do I invite my friends through Facebook and get the reward?
Last Updated: 605d