Invitation Not Being Received - Official Google Play Games Plugin

I'm making a game involving real time multiplayer (only for Android at least for now) and am not sure why my invitations are not being received on my device after I send it from another. I've dissected Google's sample game QuizRacer to see where I would be going wrong, but I can't figure it out. Would someone be able to send me the Invitation-relevant parts of their working app so I can see what I'm doing wrong?

 

i have the same problem