.xib Called Inside ViewController Does not Recognize Touch Events - ios

Question

Inside a UIViewController, I call a .xib file and present it over the current UIView.
// initiate the pop up ad view and display it
let popUpAdView = PopUpAdViewController(nibName: "PopUpAdView", bundle: nil)
popUpAdView.displayIntoSuperView(view)
There is a button inside that .xib file that should remove itself from the screen when it's touched. However it doesn't perform so.
What exactly am I missing?
class PopUpAdViewController: UIViewController {
#IBOutlet weak var popUpAdView: UIView!
#IBOutlet weak var closeButton: UIButton!
override func viewDidLoad() {
super.viewDidLoad()
// adjust the view size from the device's screen size
let screenSize = UIScreen.mainScreen().bounds
view.frame = CGRectMake(0, 64, screenSize.width, screenSize.height-64)
// cosmetically adjust the view itself
view.backgroundColor = UIColor.blackColor().colorWithAlphaComponent(0.6)
view.userInteractionEnabled = true
closeButton.userInteractionEnabled = true
// style the pop up ad view
popUpAdView.layer.cornerRadius = 5
popUpAdView.layer.shadowOpacity = 0.8
popUpAdView.layer.shadowOffset = CGSizeMake(0.0, 0.0)
closeButton.addTarget(self, action: #selector(removeOutOfSuperView), forControlEvents: .TouchUpInside)
}
func displayIntoSuperView(superView: UIView!) {
superView.addSubview(self.view)
// define the initial cosmetical values of the items
popUpAdView.transform = CGAffineTransformMakeScale(0.3, 0.3)
popUpAdView.alpha = 0.0
closeButton.alpha = 0.0
// animate...
UIView.animateWithDuration(0.8, delay: 0.0, options: .CurveEaseIn, animations: {
self.popUpAdView.alpha = 1.0
self.popUpAdView.transform = CGAffineTransformMakeScale(1.0, 1.0)
}) { (Bool) in
UIView.animateWithDuration(0.6, delay: 1.5, options: .CurveEaseIn, animations: {
self.closeButton.alpha = 1.0
}, completion: { (Bool) in
})
}
}
func removeOutOfSuperView() {
UIView.animateWithDuration(0.5, delay: 0.0, options: .CurveEaseIn, animations: {
self.closeButton.alpha = 0.0
self.popUpAdView.transform = CGAffineTransformMakeScale(0.1, 0.1)
}) { (finished) in
UIView.animateWithDuration(0.8, delay: 0.0, options: .CurveEaseIn, animations: {
self.view.alpha = 0.0
self.view.removeFromSuperview()
}, completion: nil)
}
}
#IBAction func closePopUpAdView(sender: AnyObject) {
print("Closing the pop up ad...")
removeOutOfSuperView()
}
}
Update
.xib structureL: