AdMob的横幅无法启动

Question

我没有正确运行AdMob标语，应用ID和标语。这是代码和清单：

   <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="ca-app-pub-3584974578768199~.........."/>
        <activity android:name=".ChangePassword"></activity>
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

这是代码：

import android.appcompat.app.AppCompatActivity;
import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;

import android.os.Bundle;
    public class ChangePassword extends AppCompatActivity {
    private AdView mAdView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_change_password);

        mAdView = (AdView) findViewById(R.id.adView);
        AdRequest adRequest1 = new AdRequest.Builder().build();
        mAdView.loadAd(adRequest1);

    }

}