title: Advertisement.IsReady() always return false in unity ads
body: <p>I have developed a game in unity and I have placed Unity ads in my game, but my <code>Advertisement.IsReady()</code> always return <code>false</code>. </p>
  
  <p>private string AndroidGameId = "xxxxx";</p>
  
  <pre><code>  public void ShowRewardVideo()
      {
          if (Application.internetReachability != NetworkReachability.NotReachable)
          {
              if (Advertisement.IsReady())
              {
                  Advertisement.Show("rewardedVideo", new ShowOptions() { resultCallback = HandleReward });
              }
              else
              {
                  VideoLoadingUI.SetActive(true);
                  if (!Advertisement.isInitialized)
                  {
                      Advertisement.Initialize(AndroidGameId, false);
                  }
                  StartCoroutine(waitAdLoad());
              }
          }
          else
          {
              LoadInternetFaildUI.SetActive(true);
          }
      }
      private void HandleReward(ShowResult result)
      {
          switch (result)
          {
              case ShowResult.Finished:
                  AddLifes(1);
                  break;
              case ShowResult.Skipped:
                  Advertisement.Initialize(AndroidGameId, false);
                  break;
              case ShowResult.Failed:
                  VideoLoadingUI.SetActive(false);
                  VideoLoadingUIFaild.SetActive(true);
                  Advertisement.Initialize(AndroidGameId, false);
                  break;
          }
      }
      IEnumerator waitAdLoad()
      {
          for (int i = 0; i &lt;= 5; i++)
          {
              yield return new WaitForSeconds(1f);
  
              if (Advertisement.IsReady())
              {
                  break;
              }
          }
          VideoLoadingUI.SetActive(false);
          if (Advertisement.IsReady())
          {
              Advertisement.Show("rewardedVideo", new ShowOptions() { resultCallback = HandleReward });
          }
          else
          {
             VideoLoadingUIFaild.SetActive(true);
              if (!Advertisement.isInitialized)
              {
                  Advertisement.Initialize(AndroidGameId, false);
              }
          }
      }
  </code></pre>
  
  <p>Does anyone know why this is happening?</p>