Why UIButton actions are not called when the UIButton is inside a UIScrollView

I created a panel similar to a panel containing the following buttons:

-(void)configurePanel{

self.criteriaPanel.scrollEnabled=YES;
self.criteriaPanel=[[UIScrollView alloc] initWithFrame:CGRectMake(
                                                                0.0f, 
                                                                0.0f, 
                                                                [UIScreen mainScreen].bounds.size.width,
                                                                (BUTTON_HEIGHT+(3*BUTTON_Y_OFFSET))
                                                                )];

UIView *scrollViewContent=[[UIView alloc]init];
NSArray *criteriaTypeButtonTitles=[NSArray arrayWithObjects:
                                 @"Option1",
                                 @"Option2",
                                 @"Option3",
                                 @"Option4",
                                 @"Option5",
                                 @"Option6",
                                 nil
                                 ];

for (int i=0; i<[criteriaTypeButtonTitles count]; i++) {
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
  button.tag=i;
  button.frame = CGRectMake(
                          (((BUTTON_X_OFFSET*i)+(BUTTON_WIDTH*i))+BUTTON_X_OFFSET)
                          , BUTTON_Y_OFFSET
                          , BUTTON_WIDTH
                          , BUTTON_HEIGHT
                          );  
  [button setTitle:[criteriaTypeButtonTitles objectAtIndex:i] forState:UIControlStateNormal];
  [button setTitleColor:[UIColor blueColor] forState:UIControlStateHighlighted];
  button.titleLabel.font=[UIFont systemFontOfSize:13.0f];
  [button setBackgroundColor:[UIColor grayColor]];
  [button.layer setCornerRadius:10.0f];
  [button.layer setBorderWidth:1.0f];
  [button addTarget:self action:@selector(sortByButtonTap:) forControlEvents:UIControlEventTouchDown];
  [scrollViewContent addSubview:button];
}

//based upon # of buttons
self.criteriaPanel.contentSize=CGSizeMake(
                                        (([criteriaTypeButtonTitles count]*BUTTON_WIDTH)+([criteriaTypeButtonTitles count]*BUTTON_X_OFFSET)),
                                        (BUTTON_HEIGHT+(2*BUTTON_Y_OFFSET)));
[self.criteriaPanel addSubview:scrollViewContent];
[self.view addSubview:self.criteriaPanel];
}

The panel displays correctly and scrolls, but click events (sortByButtonTap :) for buttons are never called. I suspect this is due to the buttons contained in the view contained in the scrollview. After reading a number of other questions and documents, I still cannot understand what a solution should be.

EDIT: I experimented with adding buttons to the UIScrollView (self.criteriaPanel) directly, and the taps button calls sortByButtonTap: so there’s something to do with the buttons found in scrollViewContent.