I don't know why my app doesn't show ads? - reactjs

Question

I created an app, I added react-native-admob and linked it
I changed /node_modules/react-native-admob/android/build.gradle file:
compile 'com.google.android.gms:play-services-ads:+'
to
compile 'com.google.android.gms:play-services-ads:15.0.0'
and then build the apk with "./gradlew clean && ./gradlew assembleRelease", but when I install the app in my phone it doesn't show ads.
This is my code
import {
AdMobBanner,
AdMobInterstitial,
PublisherBanner,
AdMobRewarded,
} from 'react-native-admob';
....
<View>
<AdMobBanner
adSize="fullBanner"
adUnitID="ca-app-pub-2174326550695558/6129769558"
onAdFailedToLoad={error => console.error(error)}
/>
</View>
Here is my AndroidManifest
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.brawlcalculator">
<uses-permission android:name="android.permission.INTERNET" />
<application
android:name=".MainApplication"
android:label="#string/app_name"
android:icon="#mipmap/ic_launcher"
android:roundIcon="#mipmap/ic_launcher_round"
android:allowBackup="false"
android:theme="#style/AppTheme">
<activity
android:name=".MainActivity"
android:label="#string/app_name"
android:configChanges="keyboard|keyboardHidden|orientation|screenSize"
android:windowSoftInputMode="adjustResize">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.facebook.react.devsupport.DevSettingsActivity" />
</application>
</manifest>

Answer 1

In your AndroidManifest.xml file:
Add you admob application id to a meta tag inside your application tag
<application
android:name=".MainApplication"
android:label="#string/app_name"
android:icon="#mipmap/ic_launcher"
android:roundIcon="#mipmap/ic_launcher_round"
android:allowBackup="false"
android:theme="#style/AppTheme"
> // Look at this ... after the closing tag
<meta-data
android:name="com.google.android.gms.ads.APPLICATION_ID"
android:value="ca-app-pub-2174326550695558~2753605675"
/>
</application>