InterstitialAd InvalidServerResponse“无效的XML”

Question

我正在尝试在UWP应用上显示和插页式广告，并且我从广告请求中收到错误：

• 错误代码=“InvalidServerResponse”
• 错误消息=“无效的XML”

我的代码是从https://msdn.microsoft.com/windows/uwp/monetize/interstitial-ads

复制的

        // instantiate an InterstitialAd
        InterstitialAd MyVideoAd = new InterstitialAd();

        // wire up all 4 events, see below for function templates
        MyVideoAd.AdReady += MyVideoAd_AdReady;
        MyVideoAd.ErrorOccurred += MyVideoAd_ErrorOccurred;
        MyVideoAd.Completed += MyVideoAd_Completed;
        MyVideoAd.Cancelled += MyVideoAd_Cancelled;

        var MyAppId = "d25517cb-12d4-4699-8bdc-52040c712cab";
        var MyAdUnitId = "11389925";

        // pre-fetch an ad 30-60 seconds before you need it
        MyVideoAd.RequestAd(AdType.Video, MyAppId, MyAdUnitId);

我错过了什么？