Cannot update band tab bar item value

Question

Hallo I have this code into my appDelegate:

- (void)applicationDidBecomeActive:(UIApplication *)application {

UIStoryboard* storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];
    UITabBarController *myTabBarController = [storyboard instantiateViewControllerWithIdentifier:@"tabBarController"];
    if ([unread isEqualToString:@"0"]) {
        for (UIViewController *vc in myTabBarController.viewControllers) {
            if (vc.tabBarItem.tag == 999) {
                vc.tabBarItem.badgeValue =@"5";// nil;
            }
        }
        [UIApplication sharedApplication].applicationIconBadgeNumber = 0;
}

If I test with the Debug, the code is executed in perfect way, but on the interface, the badge isn't updated.... Why?

Thanks...