Leaderboard

I'm trying to incorporate a leaderboard into my game, but I'm having some trouble.

 I have an Apple Developer account, a Sandbox tester account, and within my app on Apple Developer, I've designated that I'd like a recurring leaderboard for high scores. I selected the options presented to me (i.e. named it, assigned it an ID, set it to Best Score High-Low, integers format, singular and plural suffixes, and duration of the board before it resets).

Within Stencyl, I have the player connect to Game Center. I know this connection is happening, as when I open the app, a Game Center banner appears telling me I've connected.  I then have a leaderboard button on my main menu, which directs the player to a scene that I have designated the leaderboard scene. In my events for this scene, I have: "When game center is started: show leaderboard for [my leaderboard's ID]"

When I test this out though, and I reach the scene for leaderboard, nothing displays other than the background of the scene. There is no sign of a leaderboard. Furthermore, when I achieve a high score, it does not seem as though my game is sending the high score to game center.

Am I missing a step? Is there something I'm doing wrong?
Thanks so much for your help!!

Stencylpedia article on the subject, just in case: http://www.stencyl.com/help/view/ios-game-center/
From the article:

Scores and Achievements not showing up?
Sometimes you have to wait a few hours for the data to show up in Game Center. This seems to afflict those who are far from Apple's server farms in the US, particularly Europe.

Another common cause is that sometimes, Game Center requires that at LEAST 2 players need to submit scores for the board to show up at all.

It's been a few days since you've posted it, has the situation changed? If not, a screen shot of your code might help.