Banner Ad Without Button

I found the following 2 samples for ads (yes I turned on Test Mode), but for some reason I cannot implement the first without the use of buttons (I just want a banner to automatically be at the bottom of the page) and the other has no buttons, but does not work at all.

 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.Advertisements;
 
 public class BannerAdExample : MonoBehaviour
 {
     // For the purpose of this example, these buttons are for functionality testing:
     [SerializeField] Button _loadBannerButton;
     [SerializeField] Button _showBannerButton;
     [SerializeField] Button _hideBannerButton;
 
     [SerializeField] BannerPosition _bannerPosition = BannerPosition.BOTTOM_CENTER;
 
     [SerializeField] string _androidAdUnitId = "Banner_Android";
     [SerializeField] string _iOsAdUnitId = "Banner_iOS";
     string _adUnitId;
 
     void Awake()
     {
         //  Set banner to load automatically on awake
         //LoadBanner();
     }
 
     void Start()
     {
         
         // Disable the button until an ad is ready to show:
         _showBannerButton.interactable = false;
         _hideBannerButton.interactable = false;
 
         // Set the banner position:
         Advertisement.Banner.SetPosition(_bannerPosition);
 
         // Configure the Load Banner button to call the LoadBanner() method when clicked:
         _loadBannerButton.onClick.AddListener(LoadBanner);
         _loadBannerButton.interactable = true;
 
         // Set banner to display
         //ShowBannerAd();
     }
 
     // Implement a method to call when the Load Banner button is clicked:
     public void LoadBanner()
     {
         // Set up options to notify the SDK of load events:
         BannerLoadOptions options = new BannerLoadOptions
         {
             loadCallback = OnBannerLoaded,
             errorCallback = OnBannerError
         };
 
         // Load the Ad Unit with banner content:
         Advertisement.Banner.Load(_adUnitId, options);
     }
 
     // Implement code to execute when the loadCallback event triggers:
     void OnBannerLoaded()
     {
         Debug.Log("Banner loaded");
 
         // Configure the Show Banner button to call the ShowBannerAd() method when clicked:
         _showBannerButton.onClick.AddListener(ShowBannerAd);
         // Configure the Hide Banner button to call the HideBannerAd() method when clicked:
         _hideBannerButton.onClick.AddListener(HideBannerAd);
 
         // Enable both buttons:
         _showBannerButton.interactable = true;
         _hideBannerButton.interactable = true;
     }
 
     // Implement code to execute when the load errorCallback event triggers:
     void OnBannerError(string message)
     {
         Debug.Log($"Banner Error: {message}");
         // Optionally execute additional code, such as attempting to load another ad.
     }
 
     // Implement a method to call when the Show Banner button is clicked:
     void ShowBannerAd()
     {
         // Set up options to notify the SDK of show events:
         BannerOptions options = new BannerOptions
         {
             clickCallback = OnBannerClicked,
             hideCallback = OnBannerHidden,
             showCallback = OnBannerShown
         };
 
         // Show the loaded Banner Ad Unit:
         Advertisement.Banner.Show(_adUnitId, options);
     }
 
     // Implement a method to call when the Hide Banner button is clicked:
     void HideBannerAd()
     {
         // Hide the banner:
         Advertisement.Banner.Hide();
     }
 
     void OnBannerClicked() { }
     void OnBannerShown() { }
     void OnBannerHidden() { }
 
     void OnDestroy()
     {
         // Clean up the listeners:
         _loadBannerButton.onClick.RemoveAllListeners();
         _showBannerButton.onClick.RemoveAllListeners();
         _hideBannerButton.onClick.RemoveAllListeners();
     }
 }

//second example

 using System.Collections;
 using UnityEngine;
 using UnityEngine.Advertisements;
 
 public class Buttonless : MonoBehaviour
 {
 
     public string gameId = "1234567";
     public string placementId = "bannerPlacement";
     public bool testMode = true;
 
     void Start()
     {
         // Initialize the SDK if you haven't already done so:
         Advertisement.Initialize(gameId, testMode);
         StartCoroutine(ShowBannerWhenReady());
     }
 
     IEnumerator ShowBannerWhenReady()
     {
         while (!Advertisement.IsReady(placementId))
         {
             yield return new WaitForSeconds(0.5f);
         }
         Advertisement.Banner.Show(placementId);
     }
 }

In the first example I just put the load function in start and then added the show function and despite calling both it did not allow me to produce an ad, though with a button it does work. Can you please explain how to make a banner ad without a button?