UNITY ADS NOT SHOWING NOT EVEN THE DEMO AD SCREEN

This is my first time with unity ads, I took the code from Unity's guide. I have changed the project ID. I have followed and done everything they mentioned there. I am using the Advertisement Package from the Package Manager. Ads are also enabled in the Services section. When I click on the The button which plays the Ad it just does nothing. Also Test mode is enabled since I am in Unity only.

My code: using UnityEngine; using UnityEngine.UI; using UnityEngine.Advertisements;

[RequireComponent (typeof (Button))] public class RewardedAdsButton : MonoBehaviour, IUnityAdsListener {

 #if UNITY_IOS
 private string gameId = "";
 #elif UNITY_ANDROID
 private string gameId = "";
 #endif

 Button myButton;
 public string mySurfacingId = "rewardedVideo";

 void Start () {   
     myButton = GetComponent <Button> ();

     // Set interactivity to be dependent on the Ad Unit or legacy Placement’s status:
     myButton.interactable = Advertisement.IsReady (mySurfacingId); 

     // Map the ShowRewardedVideo function to the button’s click listener:
     if (myButton) myButton.onClick.AddListener (ShowRewardedVideo);

     // Initialize the Ads listener and service:
     Advertisement.AddListener (this);
     Advertisement.Initialize (gameId, false);
 }

 // Implement a function for showing a rewarded video ad:
 public void ShowRewardedVideo () {
     Advertisement.Show (mySurfacingId);
 }

 // Implement IUnityAdsListener interface methods:
 public void OnUnityAdsReady (string surfacingId) {
     // If the ready Ad Unit or legacy Placement is rewarded, activate the button: 
     if (surfacingId == mySurfacingId) {        
         myButton.interactable = true;
     }
 }

 public void OnUnityAdsDidFinish (string surfacingId, ShowResult showResult) {
     // Define conditional logic for each ad completion status:
     if (showResult == ShowResult.Finished) {
         // Reward the user for watching the ad to completion.
     } else if (showResult == ShowResult.Skipped) {
         // Do not reward the user for skipping the ad.
     } else if (showResult == ShowResult.Failed) {
         Debug.LogWarning ("The ad did not finish due to an error.");
     }
 }

 public void OnUnityAdsDidError (string message) {
     // Log the error.
 }

 public void OnUnityAdsDidStart (string surfacingId) {
     // Optional actions to take when the end-users triggers an ad.
 } 

}