Admob Banner Ads are not appearing after publishing my application

Question

I published my Application few days ago in Play Store, everything works perfectly, the Ads (Banner & Interstitial) were appearing as expected. But today, i discovered that the Interstitial Ads are appearing but not Banner ads. This is my first application and I don't know what may be the problem.

Answer 1

Sometimes ads are not shown due to lack of ads in google's ad inventory. You can check ad request response code to be sure.

mAdView.setAdListener(new AdListener() {
@Override
public void onAdLoaded() {
    // Code to be executed when an ad finishes loading.
}

@Override
public void onAdFailedToLoad(int errorCode) {
    // Code to be executed when an ad request fails.
    Log.d("ADMOB_ERROR_CODE", "admob error code: " + errorCode);
}

@Override
public void onAdOpened() {
    // Code to be executed when an ad opens an overlay that
    // covers the screen.
}

@Override
public void onAdLeftApplication() {
    // Code to be executed when the user has left the app.
}

@Override
public void onAdClosed() {
    // Code to be executed when when the user is about to return
    // to the app after tapping on an ad.
}
});

Further Reading: https://developers.google.com/admob/android/banner