Unity Interstitial problem

As you can see my script I disabled buttons for ads because I want them to show automatically on start but Interstitial wont show up for some reason... I enabled button and everything worked fine, but I don't want that as I said, banner works just fine... Anyone see mistake in code?? Also I try to add ShowInterstitial(); in start but it was same.....

using System; using UnityEngine; using GoogleMobileAds; using GoogleMobileAds.Api;

 public class GoogleMobileAdsDemoHandler : IInAppPurchaseHandler
 {
     private readonly string[] validSkus = { "android.test.purchased" };
     
     //Will only be sent on a success.
     public void OnInAppPurchaseFinished(IInAppPurchaseResult result)
     {
         result.FinishPurchase();
         GoogleMobileAdsDemoScript.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 GoogleMobileAdsDemoScript : MonoBehaviour
 {
     
     private BannerView bannerView;
     private InterstitialAd interstitial;
     private static string outputMessage = "";
     
     public static string OutputMessage
     {
         set { outputMessage = value; }
     }
 
     void Start(){
         RequestBanner ();
         RequestInterstitial ();
     }
 
 
     /*void OnGUI()
     {
         // Puts some basic buttons onto the screen.
         GUI.skin.button.fontSize = (int) (0.05f * Screen.height);
         GUI.skin.label.fontSize = (int) (0.025f * 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 hideBannerRect = new Rect(0.1f * Screen.width, 0.3f * Screen.height,
                                        0.8f * Screen.width, 0.1f * Screen.height);
         if (GUI.Button(hideBannerRect, "Hide Banner"))
         {
             bannerView.Hide();
         }
         
         Rect destroyBannerRect = new Rect(0.1f * Screen.width, 0.425f * 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, 0.55f * 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, 0.675f * Screen.height,
                                              0.8f * Screen.width, 0.1f * Screen.height);
         if (GUI.Button(showInterstitialRect, "Show Interstitial"))
         {
             ShowInterstitial();
         }
         
         Rect destroyInterstitialRect = new Rect(0.1f * Screen.width, 0.8f * Screen.height,
                                                 0.8f * Screen.width, 0.1f * Screen.height);
         if (GUI.Button(destroyInterstitialRect, "Destroy Interstitial"))
         {
             interstitial.Destroy();
         }
         
         Rect textOutputRect = new Rect(0.1f * Screen.width, 0.925f * Screen.height,
                                        0.8f * Screen.width, 0.05f * Screen.height);
         GUI.Label(textOutputRect, outputMessage);
     }*/
     
     private void RequestBanner()
     {
         #if UNITY_EDITOR
         string adUnitId = "unused";
         #elif UNITY_ANDROID
         string adUnitId = "ca-app-pub-8290703549707300/2896896875";
         #elif 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.BottomLeft);
         // Register for ad events.
         bannerView.AdLoaded += HandleAdLoaded;
         bannerView.AdFailedToLoad += HandleAdFailedToLoad;
         bannerView.AdOpened += HandleAdOpened;
         bannerView.AdClosing += HandleAdClosing;
         bannerView.AdClosed += HandleAdClosed;
         bannerView.AdLeftApplication += HandleAdLeftApplication;
         // Load a banner ad.
         bannerView.LoadAd(createAdRequest());
     }
     
     private void RequestInterstitial()
     {
         #if UNITY_EDITOR
         string adUnitId = "unused";
         #elif UNITY_ANDROID
         string adUnitId = "ca-app-pub-8290703549707300/4373630075";
         #elif 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.AdLoaded += HandleInterstitialLoaded;
         interstitial.AdFailedToLoad += HandleInterstitialFailedToLoad;
         interstitial.AdOpened += HandleInterstitialOpened;
         interstitial.AdClosing += HandleInterstitialClosing;
         interstitial.AdClosed += HandleInterstitialClosed;
         interstitial.AdLeftApplication += HandleInterstitialLeftApplication;
         GoogleMobileAdsDemoHandler handler = new GoogleMobileAdsDemoHandler();
         interstitial.SetInAppPurchaseHandler(handler);
         // 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();
         
     }
     
     public void ShowInterstitial()
     {
         if (interstitial.IsLoaded())
         {
             interstitial.Show();
         }
         else
         {
             print("Interstitial 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
 }