Can't post score to Game Center

jeak

I've setup a leader board using iTunes connect for my game, using this format;
com.mydom.gamename.scores

I can see the leader board in Game Center, and using the view leaderboard action. However, whenever I attempt to post a score nothing shows.
What could I be doing wrong?

I should add that when I tap post score the game centre "welcome back" notification pops up.

Thanks.