Why won't this admob ad load into my game?

This is my code:

    using System.Diagnostics;
    using System.Collections;
    using System.Collections.Generic;
    using UnityEngine;
    using GoogleMobileAds.Api;
    
    public class InterstitialScript : MonoBehaviour
    {
        private InterstitialAd interstitial;
        public static InterstitialScript instance;
        void Awake()
        {
            instance = this;
            MobileAds.Initialize(initStatus => { });
    
            if (interstitial.IsLoaded())
            {
                interstitial.Show();
            }
        }
    
        void Start()
        {
            //InterstitialScript = this;
            MobileAds.Initialize(initStatus => { });
    
            if (interstitial.IsLoaded())
            {
                interstitial.Show();
            }
        }
    
        public void RequestInterstitial()
        {
            #if UNITY_ANDROID
                string adUnitId = "ca-app-pub-9471668556390079~8501400148";
            #elif UNITY_IPHONE
                string adUnitId = null;
            #else
                string adUnitId = "unexpected_platform";
            #endif
    
            // Initialize an InterstitialAd.
            interstitial = new InterstitialAd(adUnitId);
            // Create an empty ad request.
            AdRequest request = new AdRequest.Builder().Build();
            // Load the interstitial with the request.
            if (interstitial.IsLoaded())
            {
                interstitial.LoadAd(request);
            }
            interstitial.Show();
        }
    
        void Update()
        {
            
        }
    }

I get one of those Debug.Log thing errors, that looks like this:

Here's what is reads:

No Ad Loaded

UnityEngine.Debug:Log (object)

GoogleMobileAds.Unity.InterstitialClient:Show ()

GoogleMobileAds.Api.InterstitialAd:Show ()

InterstitialScript:RequestInterstitial () (at Assets/Scripts/InterstitialScript.cs:52)

GameOver:Continue () (at Assets/Scripts/GameOver.cs:41)

UnityEngine.EventSystems.EventSystem:Update () (at

Library/PackageCache/com.unity.ugui@1.0.0/Runtime/EventSystem/EventSystem.cs:501)