interstitialWillDismissScreen only being called once - ios

Question

I am using Admob interstitials in my swift project and I am having trouble reloading the ads. The first interstitial displays fine, and when interstitialWillDismissScreen is called, it exits back to the game and reloads a new interstitial as it's supposed to. However, neither interstitialDidReceiveAd nor interstitialWillDismissScreen are called again, so after the second ad is displayed, no other ads come through. What am I missing?
import GoogleMobileAds
let appDelegate = (UIApplication.sharedApplication().delegate as! AppDelegate)
class GameScene: SKScene, GKGameCenterControllerDelegate, GADInterstitialDelegate {
var interstitial: GADInterstitial!
override func didMoveToView(view: SKView) {
//preload interstitial ad
if NSUserDefaults.standardUserDefaults().boolForKey("paidToRemoveAds") == false {
interstitial = loadAd()
}
interstitial.delegate = self
}
func gameOver() {
runGoogleAd()
}
func loadAd() -> GADInterstitial {
let ad = GADInterstitial(adUnitID: "ca-app-pub-2963481692578498/7292484569")
let request = GADRequest()
request.testDevices = [kGADSimulatorID]
ad.loadRequest(request)
return ad
}
func runGoogleAd() {
if interstitial.isReady {
interstitial.presentFromRootViewController((appDelegate.window?.rootViewController)!)
}
}
func interstitialDidReceiveAd(ad: GADInterstitial!) {
print("ad loaded")
}
func interstitialWillDismissScreen(ad: GADInterstitial!) {
interstitial = loadAd()
print("loading new ad")
}
}

Answer 1

I assume loadAd() creates a new instance? You need to set the delegate on the new instance:
func interstitialWillDismissScreen(ad: GADInterstitial!) {
interstitial = loadAd()
interstitial.delegate = self // <-- You forgot this.
print("loading new ad")
}
Actually you should probably set the delegate in loadAd() since it is an instance member of this class.