Stuck with Admob need some guidance and tips.

Hello How are you? So I created my game in unity for android. Now I am gonna use Admob to gain some money from my app. I successfully integrated admob with my unity. But I am facing one issue which is with rewarded video. It doesn't show.

The Code I am using :

 using System;
 using UnityEngine;
 using GoogleMobileAds;
 using GoogleMobileAds.Api;
 
 public class GoogleMobileAdsDemoHandler : IDefaultInAppPurchaseProcessor
 {
     private readonly string[] validSkus = { "android.test.purchased" };
 
     //Will only be sent on a success.
     public void ProcessCompletedInAppPurchase(IInAppPurchaseResult result)
     {
         result.FinishPurchase();
         Test.OutputMessage = "Purchase Succeeded! Credit user here.";
     }
 
     //Check SKU against valid SKUs.
     public bool IsValidPurchase(string sku)
     {
         foreach (string validSku in validSkus)
         {
             if (sku == validSku)
             {
                 return true;
             }
         }
         return false;
     }
 
     //Return the app's public key.
     public string AndroidPublicKey
     {
         //In a real app, return public key instead of null.
         get { return null; }
     }
 }
 
 // Example script showing how to invoke the Google Mobile Ads Unity plugin.
 public class Test : MonoBehaviour
 {
 
     private BannerView bannerView;
     private InterstitialAd interstitial;
     private RewardBasedVideoAd rewardBasedVideo;
     private float deltaTime = 0.0f;
     private static string outputMessage = "";
 
     public static string OutputMessage
     {
         set { outputMessage = value; }
     }
 
     void Start()
     {
         // Get singleton reward based video ad reference.
         rewardBasedVideo = RewardBasedVideoAd.Instance;
 
         // RewardBasedVideoAd is a singleton, so handlers should only be registered once.
         rewardBasedVideo.OnAdLoaded += HandleRewardBasedVideoLoaded;
         rewardBasedVideo.OnAdFailedToLoad += HandleRewardBasedVideoFailedToLoad;
         rewardBasedVideo.OnAdOpening += HandleRewardBasedVideoOpened;
         rewardBasedVideo.OnAdStarted += HandleRewardBasedVideoStarted;
         rewardBasedVideo.OnAdRewarded += HandleRewardBasedVideoRewarded;
         rewardBasedVideo.OnAdClosed += HandleRewardBasedVideoClosed;
         rewardBasedVideo.OnAdLeavingApplication += HandleRewardBasedVideoLeftApplication;
     }
 
     void Update()
     {
         // Calculate simple moving average for time to render screen. 0.1 factor used as smoothing
         // value.
         deltaTime += (Time.deltaTime - deltaTime) * 0.1f;
     }
 
     void OnGUI()
     {
         try
         {
 
 
             GUIStyle style = new GUIStyle();
 
             Rect rect = new Rect(0, 0, Screen.width, Screen.height);
             style.alignment = TextAnchor.LowerRight;
             style.fontSize = (int)(Screen.height * 0.06);
             style.normal.textColor = new Color(0.0f, 0.0f, 0.5f, 1.0f);
             float fps = 1.0f / deltaTime;
             string text = string.Format("{0:0.} fps", fps);
             GUI.Label(rect, text, style);
 
             // Puts some basic buttons onto the screen.
             GUI.skin.button.fontSize = (int)(0.03f * Screen.height);
 
             Rect requestBannerRect = new Rect(0.1f * Screen.width, 0.05f * Screen.height,
                                          0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(requestBannerRect, "Request Banner"))
             {
                 RequestBanner();
             }
 
             Rect showBannerRect = new Rect(0.1f * Screen.width, 0.175f * Screen.height,
                                       0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(showBannerRect, "Show Banner"))
             {
                 bannerView.Show();
             }
 
             Rect destroyBannerRect = new Rect(0.1f * Screen.width, 0.3f * Screen.height,
                                          0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(destroyBannerRect, "Destroy Banner"))
             {
                 bannerView.Destroy();
             }
 
             Rect requestInterstitialRect = new Rect(0.1f * Screen.width, 0.425f * Screen.height,
                                                0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(requestInterstitialRect, "Request Interstitial"))
             {
                 RequestInterstitial();
             }
 
             Rect showInterstitialRect = new Rect(0.1f * Screen.width, 0.55f * Screen.height,
                                             0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(showInterstitialRect, "Show Interstitial"))
             {
                 ShowInterstitial();
             }
 
             Rect requestRewardedRect = new Rect(0.1f * Screen.width, 0.675f * Screen.height,
                                            0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(requestRewardedRect, "Request Rewarded Video"))
             {
                 RequestRewardBasedVideo();
             }
 
             Rect showRewardedRect = new Rect(0.1f * Screen.width, 0.8f * Screen.height,
                                         0.8f * Screen.width, 0.1f * Screen.height);
             if (GUI.Button(showRewardedRect, "Show Rewarded Video"))
             {
                 ShowRewardBasedVideo();
             }
 
             Rect textOutputRect = new Rect(0.1f * Screen.width, 0.925f * Screen.height,
                                       1f * Screen.width, 0.1f * Screen.height);
             GUI.Label(textOutputRect, outputMessage);
         }
         catch (Exception ex)
         {
             outputMessage = ex.Message;
         }
     }
 
     private void RequestBanner()
     {
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
             string adUnitId = "hidden code";
 #elif (UNITY_5 && UNITY_IOS) || UNITY_IPHONE
             string adUnitId = "INSERT_IOS_BANNER_AD_UNIT_ID_HERE";
 #else
             string adUnitId = "unexpected_platform";
 #endif
 
         // Create a 320x50 banner at the top of the screen.
         bannerView = new BannerView(adUnitId, AdSize.SmartBanner, AdPosition.Top);
         // Register for ad events.
         bannerView.OnAdLoaded += HandleAdLoaded;
         bannerView.OnAdFailedToLoad += HandleAdFailedToLoad;
         bannerView.OnAdLoaded += HandleAdOpened;
         bannerView.OnAdClosed += HandleAdClosed;
         bannerView.OnAdLeavingApplication += HandleAdLeftApplication;
         // Load a banner ad.
         bannerView.LoadAd(createAdRequest());
     }
 
     private void RequestInterstitial()
     {
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
             string adUnitId = "hidden code";
 #elif (UNITY_5 && UNITY_IOS) || UNITY_IPHONE
             string adUnitId = "INSERT_IOS_INTERSTITIAL_AD_UNIT_ID_HERE";
 #else
             string adUnitId = "unexpected_platform";
 #endif
 
         // Create an interstitial.
         interstitial = new InterstitialAd(adUnitId);
         // Register for ad events.
         interstitial.OnAdLoaded += HandleInterstitialLoaded;
         interstitial.OnAdFailedToLoad += HandleInterstitialFailedToLoad;
         interstitial.OnAdOpening += HandleInterstitialOpened;
         interstitial.OnAdClosed += HandleInterstitialClosed;
         interstitial.OnAdLeavingApplication += HandleInterstitialLeftApplication;
         // Load an interstitial ad.
         interstitial.LoadAd(createAdRequest());
     }
 
     // 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 RequestRewardBasedVideo()
     {
 #if UNITY_EDITOR
         string adUnitId = "unused";
 #elif UNITY_ANDROID
             string adUnitId = "hidden code";
 #elif (UNITY_5 && UNITY_IOS) || UNITY_IPHONE
             string adUnitId = "INSERT_IOS_REWARD_BASED_VIDEO_AD_UNIT_ID_HERE";
 #else
             string adUnitId = "unexpected_platform";
 #endif
 
         rewardBasedVideo.LoadAd(createAdRequest(), adUnitId);
     }
 
     private void ShowInterstitial()
     {
         if (interstitial.IsLoaded())
         {
             interstitial.Show();
         }
         else
         {
             outputMessage = ("Interstitial is not ready yet.");
         }
     }
 
     private void ShowRewardBasedVideo()
     {
         if (rewardBasedVideo.IsLoaded())
         {
             rewardBasedVideo.Show();
         }
         else
         {
             outputMessage = ("Reward based video ad is not ready yet.");
         }
     }
 
     #region Banner callback handlers
 
     public void HandleAdLoaded(object sender, EventArgs args)
     {
         print("HandleAdLoaded event received.");
     }
 
     public void HandleAdFailedToLoad(object sender, AdFailedToLoadEventArgs args)
     {
         print("HandleFailedToReceiveAd event received with message: " + args.Message);
     }
 
     public void HandleAdOpened(object sender, EventArgs args)
     {
         print("HandleAdOpened event received");
     }
 
     void HandleAdClosing(object sender, EventArgs args)
     {
         print("HandleAdClosing event received");
     }
 
     public void HandleAdClosed(object sender, EventArgs args)
     {
         print("HandleAdClosed event received");
     }
 
     public void HandleAdLeftApplication(object sender, EventArgs args)
     {
         print("HandleAdLeftApplication event received");
     }
 
     #endregion
 
     #region Interstitial callback handlers
 
     public void HandleInterstitialLoaded(object sender, EventArgs args)
     {
         print("HandleInterstitialLoaded event received.");
     }
 
     public void HandleInterstitialFailedToLoad(object sender, AdFailedToLoadEventArgs args)
     {
         print("HandleInterstitialFailedToLoad event received with message: " + args.Message);
     }
 
     public void HandleInterstitialOpened(object sender, EventArgs args)
     {
         print("HandleInterstitialOpened event received");
     }
 
     void HandleInterstitialClosing(object sender, EventArgs args)
     {
         print("HandleInterstitialClosing event received");
     }
 
     public void HandleInterstitialClosed(object sender, EventArgs args)
     {
         print("HandleInterstitialClosed event received");
     }
 
     public void HandleInterstitialLeftApplication(object sender, EventArgs args)
     {
         print("HandleInterstitialLeftApplication event received");
     }
 
     #endregion
 
     #region RewardBasedVideo callback handlers
 
     public void HandleRewardBasedVideoLoaded(object sender, EventArgs args)
     {
         print("HandleRewardBasedVideoLoaded event received.");
     }
 
     public void HandleRewardBasedVideoFailedToLoad(object sender, AdFailedToLoadEventArgs args)
     {
         print("HandleRewardBasedVideoFailedToLoad event received with message: " + args.Message);
     }
 
     public void HandleRewardBasedVideoOpened(object sender, EventArgs args)
     {
         print("HandleRewardBasedVideoOpened event received");
     }
 
     public void HandleRewardBasedVideoStarted(object sender, EventArgs args)
     {
         print("HandleRewardBasedVideoStarted event received");
     }
 
     public void HandleRewardBasedVideoClosed(object sender, EventArgs args)
     {
         print("HandleRewardBasedVideoClosed event received");
     }
 
     public void HandleRewardBasedVideoRewarded(object sender, Reward args)
     {
         string type = args.Type;
         double amount = args.Amount;
         outputMessage =("HandleRewardBasedVideoRewarded event received for " + amount.ToString() + " " +
                 type);
     }
 
     public void HandleRewardBasedVideoLeftApplication(object sender, EventArgs args)
     {
         print("HandleRewardBasedVideoLeftApplication event received");
     }
 
     #endregion
 }
 

Also one more thing That I have multiple scenes. So do i have to call the request banner and bannershow every scene? Same for video and rewarded video. Thanks