Bug in invite facebook friends

[C2hWF]

I invited 3 facebook friends, but the goal in my shop is still need to invite 1 new facebook friends to unlock.

[C2hWF]

I solved the problem.
You need to connect Facebook and GameCenter.
If you don't connect GameCenter, you can't complete the goal.

[FrozenTurtle]

You shouldn't need to connect to Game Center for this. After you invited your 3 friends, did they join immediately? The task should only complete after 2 of them start playing. Can you check this on the next slot and let me know if you have any issue with unlocking it? Thanks!