My admob is not requesting ad

How come that my ad is not requesting ad to it server no reaction at all I already put the right code and install the plugin.

 using GoogleMobileAds.Api;
 …
 private BannerView bannerView;
 ...
 
 private void RequestBanner()
 {
     
         string adUnitId = "INSERT_ANDROID_BANNER_AD_UNIT_ID_HERE";
    
     // Create a 320x50 banner at the top of the screen.
     BannerView bannerView = new BannerView(adUnitId, AdSize.Banner, AdPosition.Top);
     // Create an empty ad request.
     AdRequest request = new AdRequest.Builder().Build();
     // Load the banner with the request.
     bannerView.LoadAd(request);
     bannerView.Show();
 }

Cannot even requesting ad what the best code then