You need to Follow Below Manifest Code (must have Service in manifest)
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="soapusingretrofitvolley.firebase">
<uses-permission android:name="android.permission.INTERNET"/>
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:supportsRtl="true"
android:theme="@style/AppTheme">
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<service
android:name=".MyFirebaseMessagingService">
<intent-filter>
<action android:name="com.google.firebase.MESSAGING_EVENT"/>
</intent-filter>
</service>
<service
android:name=".MyFirebaseInstanceIDService">
<intent-filter>
<action android:name="com.google.firebase.INSTANCE_ID_EVENT"/>
</intent-filter>
</service>
</application>
</manifest>