score system not working

I'm trying to have a scoring system in my game. I want to increase the score by one every time I hit a brick. The code I have now shows the score at the correct position but every time I hit a brick it doesn't increase at all. I don't really know what's going on, any help would be greatly appreciated.

I have the in my class extension. SKLabelNode *_lblScore;

This is for when my ball comes in contact with a brick.

-(void)didBeginContact:(SKPhysicsContact *)contact {

//create placeholder for the "non ball" object
SKPhysicsBody *notTheBall;

if (contact.bodyA.categoryBitMask < contact.bodyB.categoryBitMask) {
    notTheBall = contact.bodyB;
} else {
    notTheBall = contact.bodyA;
}
if (notTheBall.categoryBitMask == brickCategory) {
    //SKAction *playSFX = [SKAction playSoundFileNamed:@"brickhit.caf" waitForCompletion:NO];
    //[self runAction:playSFX];
    [_lblScore setText:[NSString stringWithFormat:@"%d", [GameState sharedInstance].score]];

    [notTheBall.node removeFromParent];
}
}

This is where I put the code for the score label.

-(instancetype)initWithSize:(CGSize)size {
if (self = [super initWithSize:size]){
    self.backgroundColor = [SKColor colorWithRed:(29.0f/255) green:(29.0f/255) blue:(29.0f/255) alpha:1.0];


    //add physics body to scene
    self.physicsBody = [SKPhysicsBody bodyWithEdgeLoopFromRect:self.frame];
    self.physicsBody.friction = 0.0f;
    self.physicsBody.categoryBitMask = edgeCategory;

    //change gravity
    self.physicsWorld.gravity = CGVectorMake(0, 0);
    self.physicsWorld.contactDelegate = self;

    // Score
    _lblScore = [SKLabelNode labelNodeWithFontNamed:@"ChalkboardSE-Bold"];
    _lblScore.fontSize = 30;
    _lblScore.fontColor = [SKColor colorWithRed:85.0f/255.0f green:191.0f/255.0f blue:154.0f/255.0f alpha:1.0];
    _lblScore.position = CGPointMake( 80, 20);
    _lblScore.horizontalAlignmentMode = SKLabelHorizontalAlignmentModeRight;
    [_lblScore setText:@"0"];
    [self addChild:_lblScore];



}
return self;
}


+ (instancetype)sharedInstance
{
static dispatch_once_t pred = 0;
static GameState *_sharedInstance = nil;

dispatch_once( &pred, ^{
    _sharedInstance = [[super alloc] init];
});
return _sharedInstance;
}

The code below I put in a separate class. It keeps the data in the phone so it keeps track of score and high score.

- (id) init
{
if (self = [super init]) {
    // Init
    _score = 0;
    _highScore = 0;

    // Load game state
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    id highScore = [defaults objectForKey:@"highScore"];
    if (highScore) {
        _highScore = [highScore intValue];
    }
}
return self;
}

- (void) saveState
{
// Update highScore if the current score is greater
_highScore = MAX(_score, _highScore);

// Store in user defaults
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:[NSNumber numberWithInt:_highScore] forKey:@"highScore"];
[[NSUserDefaults standardUserDefaults] synchronize];
}