ViewController won't appear - iOS

Question

I have an iOS Application which will load a particular view controller for authentication. However no matter what, the view controller will not load. Below is the code for my method which handles this (This is for a Game Center authentication popup):

-(void)authenticateLocalUser {

GKLocalPlayer *localPlayer = [GKLocalPlayer localPlayer];
localPlayer.authenticateHandler = ^(UIViewController *viewController, NSError *error) {

    if (viewController != nil) {
        NSLog(@"AUTH VIEW CONTROLLER");
        [[[UIApplication sharedApplication] keyWindow].rootViewController presentViewController:viewController animated:YES completion:nil];
    }

    else if (localPlayer.isAuthenticated) {
        NSLog(@"User is authenticated");
    }

    else {
        NSLog(@"Game Center Auth error.");
    }
};
}

As you can see, I have followed the official Apple developer documentation. However the output of this method is always:

Game Center Auth Error (Last NSLog).

Why doesn't the view controller ever load? Because I need it to load so that the user can login to Game Center if they haven't done so already.

Thanks for your time, Dan.

Answer 1

It turned out that the issue in the end was to do with the Game Center app itself. I just logged in/out of that and it all worked. I have also now seen this same issue replicated in other iOS apps too which use Game Center.