CloudKit: notificationChangedBlock no response

Question

I working in app using CloudKit. I'm implement a way to get deltas from CloudKit to my app (I'm using the public database). I get a response back from fetchNotificationChangesCompletionBlock block but I don't get a response back from notificationChangedBlock.

Here is my code:

-(void)checkForNewData
{
    CKServerChangeToken *token = [[cloudKitToken helper] getCloudKitToken];
    CKFetchNotificationChangesOperation *op = [[CKFetchNotificationChangesOperation alloc]
                                               initWithPreviousServerChangeToken:token];
    NSMutableArray *noteIds = [[NSMutableArray alloc] init];

    op.notificationChangedBlock = ^(CKNotification *note)
    {
        CKNotificationID *noteId = note.notificationID;
        [noteIds addObject:noteId];

        if([note isKindOfClass:[CKQueryNotification class]]) {
            CKQueryNotification *qNote = (CKQueryNotification *)note;
            CKRecordID *changedRecordID = qNote.recordID;

            NSLog(@"I got CKQueryNotification");

        }

    };

    op.fetchNotificationChangesCompletionBlock = ^(CKServerChangeToken *token, NSError *error) {

        NSLog(@"error %@", error.localizedDescription);
    };

    [[CKContainer defaultContainer] addOperation:op];
}

Any of you knows what I'm doing wrong or what is wrong with my code?

I'll really appreciate your help.