interstitial ad don't show up (AngularJs)

my app.js :

$ionicPlatform.ready(function() {
   var admobid = {};
    // select the right Ad Id according to platform
    if( /(android)/i.test(navigator.userAgent) ) { 
        admobid = { // for Android
            interstitial: 'ca-app-pub-3940256099942544/1033173712'
        };
    } else {
        admobid = { // for Windows Phone
            interstitial: 'ca-app-pub-3940256099942544/1033173712'
        };
    }

   if(window.AdMob) AdMob.prepareInterstitial({
        adId:admobid.interstitial,
        isTesting:true,
        autoShow:false
   });

my controller.js :

.controller('ChatsCtrl', function($scope, Chats) {


  $scope.$on('$ionicView.beforeEnter', function(e) {
    if (window.AdMob) AdMob.showInterstitial();
  });

  $scope.$on('$ionicView.beforeLeave', function(e) {
    if (window.AdMob) AdMob.showInterstitial();
  });

})

I'm building an ionic framework app for android and i need to add it a interstitial ad, it should run whenever user enters chats tab.

Here is my code, i copied most part of it from http://pointdeveloper.com/how-to-add-interstitial-ads-on-navigation-to-ionic-framework-apps/ .

I changed interstitial: 'ca-app-pub-3940256099942544/1033173712' parts with my own key but it didn't work. Where is the problem?

(I'm testing it in both my android phone(Nexus 5) and Genymotion android emulator)

The internal life cicle for interstitial ads when requestInterstitialAd is called is the following one, you can read more here: https://github.com/appfeel/admob-google-cordova/wiki/requestInterstitialAd

requestInterstitialAd();
options.autoShowInterstitial == true ? showInterstitial : raise(admob.events.onAdLoaded)

So if you have set options.autoShowInterstitial = true, then it should be automatically shown, otherwiese, you should call admob.requestInterstitialAd and wait for admob.events.onAdLoaded with atType === 'interstitial' to be raised. Then you should do something like:

document.addEventListener(admob.events.onAdLoaded, function (e) {
    if (e.adType === admob.AD_TYPE.INTERSTITIAL) {
        admob.showInterstitialAd();
    }
});