.

app/src/main/java/com/izouma/booster/activity/MainActivity.java

@@ -90,6 +90,7 @@ public class MainActivity extends AppCompatActivity {
                 // The mInterstitialAd reference will be null until
                 // an ad is loaded.
                 Log.i("ad", "onAdLoaded");
+                interstitialAd.show(MainActivity.this);
             }
 
             @Override