private void OnInterstitialAdFailedToOpenHandler(string reason)
{
DDNASmartAds.Instance.OnInterstitialAdOpened -= this.OnInterstitialAdOpenedHandler;
DDNASmartAds.Instance.OnInterstitialAdFailedToOpen -= this.OnInterstitialAdFailedToOpenHandler;
DDNASmartAds.Instance.OnInterstitialAdClosed -= this.OnInterstitialAdClosedHandler;
if (this.OnInterstitialAdFailedToOpen != null) {
this.OnInterstitialAdFailedToOpen(reason);
}
}