[Solved] Google Admob "Missing Application ID" Error

Add meta-data below <application> tag

 

ex

 <application
        android:label="myApplication"
        android:name="${applicationName}"
        android:icon="@mipmap/ic_launcher"
        android:usesCleartextTraffic="true">
        <meta-data
            android:name="com.google.android.gms.ads.APPLICATION_ID"
            android:value="ca-app-pub-===Yours====" />
        <activity
            android:name=".MainActivity"

 

Not inside <activity> tag