Admob横幅广告不能使用我的广告单元ID，但可以使用虚拟ID工作正常吗？

Question

我正在尝试通过官方博客上的教程将Ad Mob与xamarin android集成。它可以正常使用虚拟ID，但不适用于我的广告单元ID。

这是我的MainActivity.cs

  public class MainActivity : Activity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);


        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);
        var id = "ca-app-pub-*******************";
        Android.Gms.Ads.MobileAds.Initialize(ApplicationContext, id);
        var adView = FindViewById<AdView>(Resource.Id.adView);
        var adRequest = new AdRequest.Builder().Build();
        adView.LoadAd(adRequest);
    }
}

Main.axml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:minWidth="25px"
android:minHeight="25px">
<com.google.android.gms.ads.AdView xmlns:ads="http://schemas.android.com/apk/res-auto"
    android:id="@+id/adView"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    ads:adSize="SMART_BANNER"
    ads:adUnitId="@string/banner_ad_unit_id" />
</LinearLayout>

的strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="app_name">App2</string>
<string name="banner_ad_unit_id">ca-app-pub-3940256099942544/6300978111</string> <!--this works-->
 <!--<string name="banner_ad_unit_id">ca-app-pub-
  6656166334594340/1253040688</string>--> <!--this dont-->
  </resources>

的AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="App2.App2" android:versionCode="1" android:versionName="1.0" android:installLocation="auto">
    <uses-sdk android:minSdkVersion="21" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <application android:allowBackup="true" android:label="@string/app_name">
      <activity android:name="com.google.android.gms.ads.AdActivity"
                android:configChanges="keyboard|keyboardHidden|orientation|screenLayout|uiMode|screenSize|smallestScreenSize"
                android:theme="@android:style/Theme.Translucent" />
  </application>
</manifest>