Pause Script set script when home button is pressed

I was wondering how I can pause the sprite set scene when the home button is pressed.

I found some answers here and tried it with a notification center like this.

When my scene loads:

 [[NSNotificationCenter defaultCenter]
          addObserver:self
          selector:@selector(applicationDidEnterBackground)
          name:UIApplicationDidEnterBackgroundNotification
          object:nil];

      

        
        
        
      

    

And then later on, a method that gets called if it enters the background:

 - (void) applicationDidEnterBackground{
     NSLog(@"Enter to background");
     self.scene.view.paused  =YES;
 }

      

        
        
        
      

    

The problem is I am getting the NSLog message so the applicationDidEnterBackground method is being called correctly. But the problem is, when I go back to the application, my application is not paused.

So my pause statement (self.scene.view.paused = YES;) is not getting called?

If I put the exact expression somewhere else in the code, or if I make a pause button with that expression, then the pause works fine.

What is the problem? Why won't this work with Action Center?