unity app crashes when admob banner ad is requested but works fine for interstitial and video ad

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

public class AddManager : MonoBehaviour { private string APP_ID = “--------------"; private BannerView bannerAD; private InterstitialAd interstitialAd; private RewardBasedVideoAd rewardVideoAd;

 void Start()
 {
     //MobileAds.Initialize(APP_ID);
     RequestBanner();
     RequestInterstitial();
     RequestVideoAD();
 }
 void RequestBanner()
 {
     string banner_ID = "ca-app-pub-3940256099942544/6300978111";
     bannerAD = new BannerView(banner_ID,AdSize.SmartBanner, AdPosition.Top);
     AdRequest adRequest = new AdRequest.Builder().AddTestDevice("2077ef9a63d2b398840261c8221a0c9b").Build();
     bannerAD.LoadAd(adRequest);
 }
 void RequestInterstitial()
 {
     string interstitial_ID = "ca-app-pub-3940256099942544/1033173712";
     interstitialAd = new InterstitialAd(interstitial_ID);
     //for real app
     // Adrequest adRequest = new Adrequest.Builder();
     //for testing
     AdRequest adRequest = new AdRequest.Builder().AddTestDevice("2077ef9a63d2b398840261c8221a0c9b").Build();
     interstitialAd.LoadAd(adRequest);
 }
 void RequestVideoAD()
 {
     string video_ID = "ca-app-pub-3940256099942544/5224354917";
     rewardVideoAd = RewardBasedVideoAd.Instance;
     //for real app
     // Adrequest adRequest = new Adrequest.Builder();
     //for testing
     AdRequest adRequest = new AdRequest.Builder().AddTestDevice("2077ef9a63d2b398840261c8221a0c9b").Build();
     rewardVideoAd.LoadAd(adRequest, video_ID);
 }
 public void Display_Banner()
 {
     bannerAD.Show();
 }
 public void Display_InterstitalAD()
 {
     if(interstitialAd.IsLoaded())
     {
         interstitialAd.Show();
     }
 }
 public void Display_Reward_Video()
 {
     if(rewardVideoAd.IsLoaded())
     {
         rewardVideoAd.Show();
     }
 },