Unity Admob didint show in android device

My admob its show with older admob plugin but now with newest admob plugin didint show can someone help me here my code:

Android Manifest:

 <?xml version="1.0" encoding="utf-8"?>
 <!--
 This Google Mobile Ads plugin library manifest will get merged with your
 application's manifest, adding the necessary activity and permissions
 required for displaying ads.
 -->
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     package="com.google.unity.ads"
     android:versionName="1.0"
     android:versionCode="1">
   <uses-sdk android:minSdkVersion="14"
       android:targetSdkVersion="19" />
   <application>
   <!-- Your AdMob App ID will look similar to this sample ID:
     ca-app-pub-3940256099942544~3347511713 -->
     <meta-data
     android:name="com.google.android.gms.ads.com.racingcar"
     android:value="[ca-app-pub-3940256099942544~3347511713]"/>
   </application>
 </manifest>

Admob script

 using GoogleMobileAds;
 using GoogleMobileAds.Api;
 
 // Example script showing how to invoke the Google Mobile Ads Unity plugin.
 public class AdmobManager: MonoBehaviour
 {
     private BannerView bannerView;
     private InterstitialAd interstitial;
     private RewardedAd rewardedAd;
 
     public void Start()
     {
 
 #if UNITY_ANDROID
         string appId = "ca-app-pub-3940256099942544~3347511713";
 #elif UNITY_IPHONE
         string appId = "ca-app-pub-3940256099942544~1458002511";
 #else
         string appId = "unexpected_platform";
 #endif
 
         MobileAds.SetiOSAppPauseOnBackground(true);
 
         // Initialize the Google Mobile Ads SDK.
         MobileAds.Initialize(appId);
 
         this.CreateAndLoadRewardedAd();
         this.RequestBanner();
         this.RequestInterstitial();
 
     }
 
     // Returns an ad request with custom ad targeting.
     private AdRequest CreateAdRequest()
     {
         return new AdRequest.Builder()
             .AddTestDevice(AdRequest.TestDeviceSimulator)
             .AddTestDevice("0123456789ABCDEF0123456789ABCDEF")
             .AddKeyword("game")
             .SetGender(Gender.Male)
             .SetBirthday(new DateTime(1985, 1, 1))
             .TagForChildDirectedTreatment(false)
             .AddExtra("color_bg", "9B30FF")
             .Build();
     }
 
     private void RequestBanner()
     {
         // These ad units are configured to always serve test ads.
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
         string adUnitId = "ca-app-pub-3940256099942544/6300978111";
 #elif UNITY_IPHONE
         string adUnitId = "ca-app-pub-3940256099942544/2934735716";
 #else
         string adUnitId = "unexpected_platform";
 #endif
 
         // Clean up banner ad before creating a new one.
         if (this.bannerView != null)
         {
             this.bannerView.Destroy();
         }
 
         // Create a 320x50 banner at the top of the screen.
         this.bannerView = new BannerView(adUnitId, AdSize.SmartBanner, AdPosition.Top);
 
         // Register for ad events.
         this.bannerView.OnAdLoaded += this.HandleAdLoaded;
         this.bannerView.OnAdFailedToLoad += this.HandleAdFailedToLoad;
         this.bannerView.OnAdOpening += this.HandleAdOpened;
         this.bannerView.OnAdClosed += this.HandleAdClosed;
         this.bannerView.OnAdLeavingApplication += this.HandleAdLeftApplication;
 
         // Load a banner ad.
         this.bannerView.LoadAd(this.CreateAdRequest());
     }
 
     private void RequestInterstitial()
     {
         // These ad units are configured to always serve test ads.
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
         string adUnitId = "ca-app-pub-3940256099942544/1033173712";
 #elif UNITY_IPHONE
         string adUnitId = "ca-app-pub-3940256099942544/4411468910";
 #else
         string adUnitId = "unexpected_platform";
 #endif
 
         // Clean up interstitial ad before creating a new one.
         if (this.interstitial != null)
         {
             this.interstitial.Destroy();
         }
 
         // Create an interstitial.
         this.interstitial = new InterstitialAd(adUnitId);
 
         // Register for ad events.
         this.interstitial.OnAdLoaded += this.HandleInterstitialLoaded;
         this.interstitial.OnAdFailedToLoad += this.HandleInterstitialFailedToLoad;
         this.interstitial.OnAdOpening += this.HandleInterstitialOpened;
         this.interstitial.OnAdClosed += this.HandleInterstitialClosed;
         this.interstitial.OnAdLeavingApplication += this.HandleInterstitialLeftApplication;
 
         // Load an interstitial ad.
         this.interstitial.LoadAd(this.CreateAdRequest());
     }
 
     public void CreateAndLoadRewardedAd()
     {
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
         string adUnitId = "ca-app-pub-3940256099942544/5224354917";
 #elif UNITY_IPHONE
         string adUnitId = "ca-app-pub-3940256099942544/1712485313";
 #else
         string adUnitId = "unexpected_platform";
 #endif
         // Create new rewarded ad instance.
         this.rewardedAd = new RewardedAd(adUnitId);
 
         // Called when an ad request has successfully loaded.
         this.rewardedAd.OnAdLoaded += HandleRewardedAdLoaded;
         // Called when an ad request failed to load.
         this.rewardedAd.OnAdFailedToLoad += HandleRewardedAdFailedToLoad;
         // Called when an ad is shown.
         this.rewardedAd.OnAdOpening += HandleRewardedAdOpening;
         // Called when an ad request failed to show.
         this.rewardedAd.OnAdFailedToShow += HandleRewardedAdFailedToShow;
         // Called when the user should be rewarded for interacting with the ad.
         this.rewardedAd.OnUserEarnedReward += HandleUserEarnedReward;
         // Called when the ad is closed.
         this.rewardedAd.OnAdClosed += HandleRewardedAdClosed;
 
         // Create an empty ad request.
         AdRequest request = this.CreateAdRequest();
         // Load the rewarded ad with the request.
         this.rewardedAd.LoadAd(request);
     }
 
     private void ShowInterstitial()
     {
         if (this.interstitial.IsLoaded())
         {
             this.interstitial.Show();
         }
         else
         {
             MonoBehaviour.print("Interstitial is not ready yet");
         }
     }
 
     private void ShowRewardedAd()
     {
         if (this.rewardedAd.IsLoaded())
         {
             this.rewardedAd.Show();
         }
         else
         {
             MonoBehaviour.print("Rewarded ad is not ready yet");
         }
     }
 
     #region Banner callback handlers
 
     public void HandleAdLoaded(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleAdLoaded event received");
     }
 
     public void HandleAdFailedToLoad(object sender, AdFailedToLoadEventArgs args)
     {
         MonoBehaviour.print("HandleFailedToReceiveAd event received with message: " + args.Message);
     }
 
     public void HandleAdOpened(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleAdOpened event received");
     }
 
     public void HandleAdClosed(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleAdClosed event received");
     }
 
     public void HandleAdLeftApplication(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleAdLeftApplication event received");
     }
 
     #endregion
 
     #region Interstitial callback handlers
 
     public void HandleInterstitialLoaded(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleInterstitialLoaded event received");
     }
 
     public void HandleInterstitialFailedToLoad(object sender, AdFailedToLoadEventArgs args)
     {
         MonoBehaviour.print(
             "HandleInterstitialFailedToLoad event received with message: " + args.Message);
     }
 
     public void HandleInterstitialOpened(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleInterstitialOpened event received");
     }
 
     public void HandleInterstitialClosed(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleInterstitialClosed event received");
     }
 
     public void HandleInterstitialLeftApplication(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleInterstitialLeftApplication event received");
     }
 
     #endregion
 
     #region RewardedAd callback handlers
 
     public void HandleRewardedAdLoaded(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleRewardedAdLoaded event received");
     }
 
     public void HandleRewardedAdFailedToLoad(object sender, AdErrorEventArgs args)
     {
         MonoBehaviour.print(
             "HandleRewardedAdFailedToLoad event received with message: " + args.Message);
     }
 
     public void HandleRewardedAdOpening(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleRewardedAdOpening event received");
     }
 
     public void HandleRewardedAdFailedToShow(object sender, AdErrorEventArgs args)
     {
         MonoBehaviour.print(
             "HandleRewardedAdFailedToShow event received with message: " + args.Message);
     }
 
     public void HandleRewardedAdClosed(object sender, EventArgs args)
     {
         MonoBehaviour.print("HandleRewardedAdClosed event received");
     }
 
     public void HandleUserEarnedReward(object sender, Reward args)
     {
         string type = args.Type;
         double amount = args.Amount;
         MonoBehaviour.print(
             "HandleRewardedAdRewarded event received for "
                         + amount.ToString() + " " + type);
     }
 
     #endregion
 }