iAd does not show the "You're Connected" banner

Question

I've used iAd in my project. But my bannerView is not showing anything The bannerView is just showing a white background.

import UIKit
import iAd

class ParentTransfersViewController: UIViewController, ADBannerViewDelegate {
    @IBOutlet weak var bannerView: ADBannerView!
    override func viewDidLoad() {
        super.viewDidLoad()
        bannerView.delegate = self
    }
}