how to make this code in google play closed test

Question

this code is perfectly working in unity editor but when I try it in google play closed test it does not work because there are no ad displayed so my bool to pause my player stay true and the player did not move

        public class InterstitialAd : MonoBehaviour
   {
       public string androidAdUnitId;
       public string iosAdUnitId;
       IInterstitialAd interstitialAd;

       async void Start()
       {
           // Initialize the package to access API
           await UnityServices.InitializeAsync();

           // Instantiate an interstitial ad object with platform
           if (Application.platform == RuntimePlatform.Android)
           {
               interstitialAd = MediationService.Instance.CreateI
           }
           else if (Application.platform == RuntimePlatform.IPhon
           {
               interstitialAd = MediationService.Instance.CreateI
           }
if UNITY_EDITOR
           else
           {
               interstitialAd = MediationService.Instance.CreateI
           }
endif

           // Subscribe callback methods to load events:
           interstitialAd.OnLoaded += AdLoaded;
           interstitialAd.OnFailedLoad += AdFailedToLoad;

           // Subscribe callback methods to show events:
           interstitialAd.OnShowed += AdShown;
           interstitialAd.OnFailedShow += AdFailedToShow;
           interstitialAd.OnClosed += AdClosed;
           interstitialAd.Load();
           Debug.Log("try LoadAd");
       }

 private void AdClosed(object sender, EventArgs e)
 {
     Debug.Log("Ad has closed");
     StartBTNBehaviour.pause = false; //this bool control the player movement false = player 
                                      //move
     // Execute logic after an ad has been closed.
 }

 public void ShowAd()
 {
     // Ensure the ad has loaded, then show it.
     Debug.Log("try ShowAd");
     if (interstitialAd.AdState == AdState.Loaded)
     {
         interstitialAd.Show();
         Debug.Log("ShowAd");
     }
     else
     {
         Debug.Log("Failed ShowAd");
         StartBTNBehaviour.pause = false; //added to test 
     }

so my problem is no ads in google closed test which make my pause bool not changed