How to show ProgressBar With AFNetworking AFHTTPRequestOperationManager

I am trying to show the Progress Bar as I download a JSON from a url. The JSON is downloading correctly but I am not sure how to show the Progress Bar. I have tried using UIProgressView but it does not display on the screen. Any suggestions would be appreciated.

CGFloat width = [UIScreen mainScreen].bounds.size.width;
CGFloat height = [UIScreen mainScreen].bounds.size.height;

CGRect rect = CGRectMake(width/2, height/2, width/5, height/5);
UIProgressView *myProgressView = [[UIProgressView alloc]initWithFrame:rect];
myProgressView.progressViewStyle = UIProgressViewStyleBar;
[self.view addSubview:myProgressView];

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];    
[manager GET:@"https:urlWithJson" parameters:nil success:^(AFHTTPRequestOperation *operation, id responseObject) {
      [operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead)
       {
           myProgressView.progress = (float)totalBytesRead / totalBytesExpectedToRead;
       }];
      [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
          NSLog(@"operation Completed");
      } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
          NSLog(@"ERROR");
      }];

      [operation start];
  } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
      NSLog(@"timeout Error: %@", error);
  }];