why isn't my ad screen appearing?

i get the debug.log printed to console but it isn't showing anything on screen

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4. using UnityEngine.Advertisements;
5.  
6. public class AdsController : MonoBehaviour
7. {
8.     string playstoreID = "3403842";
9.     string videoAd = "video";
10.     bool testMode = true;
11.  
12.     [SerializeField] LivesManager deathCounter;
13.  
14.     // Start is called before the first frame update
15.     void Start()
16.     {
17.         deathCounter = FindObjectOfType<LivesManager>();
18.         Advertisement.Initialize(playstoreID, testMode);
19.     }
20.  
21.     // Update is called once per frame
22.     void Update()
23.     {
24.        InitializeMonetization();
25.     }
26.  
27.     public void InitializeMonetization()
28.     {
29.         if (deathCounter.deathCounter == 3)
30.         {          
31.             PlayAd();
32.         }
33.     }
34.  
35.     public void PlayAd()
36.     {      
37.             Debug.Log("ad");
38.             Advertisement.Show("video");
39.             deathCounter.deathCounter = 0;
40.     }
41. }
42.