title: Admob banner is not showing up
body: <p>My admob banner is not showing up, I have gone through the guide found here
  <a href="https://firebase.google.com/docs/admob/android/quick-start" rel="noreferrer">https://firebase.google.com/docs/admob/android/quick-start</a></p>
  
  <p>MainActivity</p>
  
  <pre><code>private AdView mAdView;
  
  @Override
  protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      MobileAds.initialize(getApplicationContext(), "ca-app-pub-3940256099942544/6300978111");
      mAdView = (AdView) findViewById(R.id.adView);
      AdRequest adRequest = new AdRequest.Builder().build();
      mAdView.loadAd(adRequest);
  }
  </code></pre>
  
  <p>Layout</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
      xmlns:tools="http://schemas.android.com/tools"
      xmlns:ads="http://schemas.android.com/apk/res-auto"
      android:id="@+id/activity_main"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:paddingBottom="@dimen/activity_vertical_margin"
      android:paddingLeft="@dimen/activity_horizontal_margin"
      android:paddingRight="@dimen/activity_horizontal_margin"
      android:paddingTop="@dimen/activity_vertical_margin"
      tools:context="com.example.myapplication.MainActivity"&gt;
  
      &lt;TextView
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:text="Hello World!" /&gt;
  
      &lt;com.google.android.gms.ads.AdView
          android:id="@+id/adView"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:layout_centerHorizontal="true"
          android:layout_alignParentBottom="true"
          ads:adSize="BANNER"
          ads:adUnitId="ca-app-pub-3940256099942544/6300978111"&gt;
      &lt;/com.google.android.gms.ads.AdView&gt;
  &lt;/RelativeLayout&gt;
  </code></pre>
  
  <p>In my Manifest, I have this permission</p>
  
  <pre><code>&lt;uses-permission android:name="android.permission.INTERNET" /&gt;
  </code></pre>
  
  <p>Project Gradle</p>
  
  <pre><code>buildscript {
      repositories {
          jcenter()
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:2.2.3'
  
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
          classpath 'com.google.gms:google-services:3.0.0'
      }
  }
  
  allprojects {
      repositories {
          jcenter()
      }
  }
  
  task clean(type: Delete) {
      delete rootProject.buildDir
  }
  </code></pre>
  
  <p>app gradle</p>
  
  <pre><code>apply plugin: 'com.android.application'
  
  android {
      compileSdkVersion 25
      buildToolsVersion "25.0.2"
      defaultConfig {
          applicationId "com.example.myapplication"
          minSdkVersion 16
          targetSdkVersion 25
          versionCode 1
          versionName "1.0"
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
      }
      buildTypes {
          release {
              minifyEnabled false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  }
  
  dependencies {
      compile fileTree(dir: 'libs', include: ['*.jar'])
      androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
          exclude group: 'com.android.support', module: 'support-annotations'
      })
      compile 'com.android.support:appcompat-v7:25.1.1'
      compile 'com.google.firebase:firebase-ads:10.0.1'
      compile 'com.google.firebase:firebase-core:10.0.1'
      testCompile 'junit:junit:4.12'
  }
  
  
  
  apply plugin: 'com.google.gms.google-services'
  </code></pre>
  
  <p>Log</p>
  
  <pre><code>01-31 20:44:49.586 3556-3556/? D/ucsBai_ConnectionManager: mPackageReceiver Action android.intent.action.PACKAGE_ADDED
  01-31 20:44:58.836 19607-19607/com.example.myapplication I/FA: App measurement is starting up, version: 10084
  01-31 20:44:58.836 19607-19607/com.example.myapplication I/FA: To enable debug logging run: adb shell setprop log.tag.FA VERBOSE
  01-31 20:44:58.836 19607-19607/com.example.myapplication D/FA: Debug-level message logging enabled
  01-31 20:44:58.836 19607-19607/com.example.myapplication D/FA: AppMeasurement singleton hash: 23949389
  01-31 20:44:58.846 19607-19607/com.example.myapplication V/FA: Collection enabled
  01-31 20:44:58.846 19607-19607/com.example.myapplication V/FA: App package, google app id: com.example.myapplication, 1:665936977222:android:13c3c6a65bcbec53
  01-31 20:44:58.846 19607-19607/com.example.myapplication I/FA: To enable faster debug mode event logging run:
                                                                   adb shell setprop debug.firebase.analytics.app com.example.myapplication
  01-31 20:44:58.906 19607-19607/com.example.myapplication V/FA: Registered activity lifecycle callback
  01-31 20:44:58.916 19607-20434/com.example.myapplication V/FA: Using measurement service
  01-31 20:44:58.916 19607-20434/com.example.myapplication V/FA: Connecting to remote service
  01-31 20:44:59.816 19607-20434/com.example.myapplication V/FA: Connection attempt already in progress
  01-31 20:45:00.116 19607-20434/com.example.myapplication D/FA: Connected to remote service
  01-31 20:45:00.116 19607-20434/com.example.myapplication V/FA: Processing queued up service tasks: 2
  01-31 20:45:05.156 19607-20434/com.example.myapplication V/FA: Inactivity, disconnecting from the service
  </code></pre>