Admob rewarded video ads problem

I put rewarded video ads to my unity game and it works, i can see the video in my phone.
The only problem is that i cant control the rewarded video events, I tried to do that when a player finishes to watch the video he will get more coins and also that the video ad button wont be activated:

public void HandleRewardBasedVideoRewarded(object sender, Reward args)
    {
        videoButton.SetActive(false);
        valueScore += PlayerPrefs.GetInt("Currency");
        PlayerPrefs.SetInt("Currency", valueScore);
        alreadyShowedVideo = true;
        gotCoinsText.text = "You got more coins!";
    }

btw I also put the handlers in Start function

 void Start()
{
this.rewardBasedVideo = RewardBasedVideoAd.Instance;
        this.rewardBasedVideo.OnAdLoaded += this.HandleRewardBasedVideoLoaded;
        this.rewardBasedVideo.OnAdFailedToLoad += this.HandleRewardBasedVideoFailedToLoad;
        this.rewardBasedVideo.OnAdOpening += this.HandleRewardBasedVideoOpened;
        this.rewardBasedVideo.OnAdStarted += this.HandleRewardBasedVideoStarted;
        this.rewardBasedVideo.OnAdRewarded += this.HandleRewardBasedVideoRewarded;
        this.rewardBasedVideo.OnAdClosed += this.HandleRewardBasedVideoClosed;
        this.rewardBasedVideo.OnAdLeavingApplication += this.HandleRewardBasedVideoLeftApplication;
}

For some reason when i finish watching the video I dont get more coins and I can still see the video button.

Download those files from Admob Unity3d Plugin Project Home https://github.com/unity-plugins/Unity-Admob or Download all the Unity admob plugin project https://github.com/unity-plugins/Unity-Admob/archive/master.zip

Installation Admob Unity

Open your project in the Unity editor. Navigate to Assets → Import Package → Custom Package. Select the AdmobUnityPlugin.unitypackage file. Import all of the files for the plugins by selecting Import. Make sure to check for any conflicts with files

Init Admob Unity Plugin

Create A C# script ,drag the script to a object on scene , add the follow code in the script file

 using admob;
 Admob.Instance().initAdmob("admob banner id", "admob interstitial id");//admob id with format ca-app-pub-279xxxxxxxx/xxxxxxxx
 //Admob.Instance().initAdmob("ca-app-pub-3940256099942544/2934735716", "ca-app-pub-3940256099942544/4411468910");

Here is the minimal code to create an admob video.

 Admob.Instance().loadRewardedVideo("ca-app-pub-3940256099942544/1712485313"); 

video need to be explicitly shown at an appropriate stopping point in your app, check that the video is ready before showing it:

 if (Admob.Instance().isRewardedVideoReady()) {
   Admob.Instance().showRewardedVideo();
 }

this.rewardBasedVideo.OnAdRewarded += this.HandleRewardBasedVideoRewarded;
write this line right upper where you are showing ad.