I have create a Unity game, 1st I add an AdMob interstitial ads script on game object then try on my main camera when I test in my mobile before publishing. It has worked like real time ads and mistakenly clicked it and earn 0.3 so I create new ad unit placed it on my game then published my game. But the ads are not showing in real time. No error was found in AdMob but 147 ad requests are shown in AdMob and ads are not visible when my game 1st scene opens.

Here is my interstitial ads script code:

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

public class AdmobScript : MonoBehaviour
{
   private InterstitialAd interstitial;

   private void RequestInterstitial()
   {
      #if UNITY_ANDROID
         string adUnitId = "ca-app-pub-3129337025883034/9036322***";
      #elif UNITY_IPHONE
         string adUnitId = "INSERT_IOS_INTERSTITIAL_AD_UNIT_ID_HERE";
      #else
         string adUnitId = "unexpected_platform";
      #endif

      // Create an interstitial.
      this.interstitial = new InterstitialAd(adUnitId);
      // Load an interstitial ad.
      this.interstitial.LoadAd(this.CreateAdRequest());
   }

   // Returns an ad request
   private AdRequest CreateAdRequest()
   {
      return new AdRequest.Builder().Build();
   }

   private void ShowInterstitial()
   {
      if (interstitial.IsLoaded())
      {
         interstitial.Show();
      }
   }

   public void Start()
   {
      RequestInterstitial();
   }

   void Gameover()
   {
      if(interstitial.isloaded){
        ShowInterstitial();
      }
   }
}