 <p>Some comments requested further details about what I commented out to resolve this issue. I didn't think this was good to add as an edit to the question, since it specifically goes over the resolution. It's been a while since I've worked on this project, so it's not all at the top of my head &amp; I'm not sure I've done everything correctly ... I'll do my best to explain it, though.</p> <p>In the file <code>GameCenterManager.h</code>, it looks like <code>authenticateLocalUser</code> is being initialized:</p> <p><code>- (void) authenticateLocalUser;</code></p> <p>In the file <code>App_NameViewController.m</code>, <code>viewDidLoad</code> is checking to see if Game Center is available:</p> <pre><code>self.currentLeaderBoard = kLeaderboardID; if ([GameCenterManager isGameCenterAvailable]) { self.gameCenterManager = [[[GameCenterManager alloc] init] autorelease]; [self.gameCenterManager setDelegate:self]; [self.gameCenterManager authenticateLocalUser]; } else { // The current device does not support Game Center. } </code></pre> <p>In the file <code>GameCenterManager.m</code></p> <pre><code>- (void) authenticateLocalUser { if([GKLocalPlayer localPlayer].authenticated == NO) { [[GKLocalPlayer localPlayer] authenticateWithCompletionHandler:^(NSError *error) { // report any unreported scores or achievements [self retrieveScoresFromDevice]; [self retrieveAchievementsFromDevice]; //[self callDelegateOnMainThread: @selector(processGameCenterAuth:) withArg: NULL error: error]; }]; } } </code></pre> <p>The line that I commented out, which moved me past the <code>Missed Method</code> error, was:</p> <p><code>[self callDelegateOnMainThread: @selector(processGameCenterAuth:) withArg: NULL error: error];</code></p> <p>I hope this helps!</p>