Make sure that both you and your friend/s have finished the Prologue levels of the game. If they haven't completed this and then returned to the main screen, your reward will not be unlocked. So make sure after your friends complete the Prologue, that they go back to the main screen to trigger the rewards.

While connected to the internet, shut down the game and have your friend/s do the same, then reopen the game and go to the main screen. This will make your game sync and should trigger the rewards if you don’t have them.

This one is kind of a simple check, but make sure your connection to the internet is strong and stable.