The Firebase Database don't get updated even after sending messages

Question

The code is supposed to allow the user to send a message and the message is supposed to be stored in firebase data base but instead I'm getting a firebase warning and nothing is added to the database. I have an authentication part in the code and it's working perfectly fine so I am wondering what might be wrong.

EDIT: I have already tried this answer before: https://stackoverflow.com/a/39480273/7310034

The firebase warning:

E/FA: AppMeasurementReceiver not registered/enabled
E/FA: AppMeasurementService not registered/enabled
E/FA: Uploading is not possible. App measurement disabled

The AndroidManifest.xml :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.google.firebase.udacity.friendlychat">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <service
            android:name="com.google.android.gms.measurement.AppMeasurementService"
            android:enabled="true"
            android:exported="false" />

        <receiver
            android:name="com.google.android.gms.measurement.AppMeasurementReceiver"
            android:enabled="true">
            <intent-filter>
                <action android:name="com.google.android.gms.measurement.UPLOAD" />
                <action android:name="com.android.vending.INSTALL_REFERRER"/>
            </intent-filter>
        </receiver>
        <activity android:name="com.google.firebase.udacity.friendlychat.MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>

</manifest>

The MainActivity code involved:

@Override
    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mUsername = ANONYMOUS;

        mFirebaseDatabase =  FirebaseDatabase.getInstance();
        mFirebaseAuth = FirebaseAuth.getInstance();
        mFirebaseStorage = FirebaseStorage.getInstance();

        mMessagesDatabaseReference = mFirebaseDatabase.getReference().child("messages");
        mChatPhotoStorageReference = mFirebaseStorage.getReference().child("chat_photos");


        // Initialize references to views
        mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
        mMessageListView = (ListView) findViewById(R.id.messageListView);
        mPhotoPickerButton = (ImageButton) findViewById(R.id.photoPickerButton);
        mMessageEditText = (EditText) findViewById(R.id.messageEditText);
        mSendButton = (Button) findViewById(R.id.sendButton);



        // Initialize message ListView and its adapter
        List<FriendlyMessage> friendlyMessages = new ArrayList<>();
        mMessageAdapter = new MessageAdapter(this, R.layout.item_message, friendlyMessages);
        mMessageListView.setAdapter(mMessageAdapter);

        // Initialize progress bar
        mProgressBar.setVisibility(ProgressBar.INVISIBLE);

  // Send button sends a message and clears the EditText
        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Log.e("I am on click ","and adding a ten");
                // This object has all the keys that we’ll store as a message in the realtime database.
                FriendlyMessage friendlyMessage = new FriendlyMessage(mMessageEditText.getText().toString(), mUsername, null);
                Log.e("I am on click ","and adding a 999999");
                mMessagesDatabaseReference.push().setValue(friendlyMessage);
                Log.e(String.valueOf(friendlyMessage),"    Surprise!        ");
                // Clear input box
                mMessageEditText.setText("");
            }
        });