Data is not getting added to Firebase Realtime Database [duplicate]

Question

I've been following this Tutorial for the Realtime Database, this tutorial was last Updated 31 Dec 2020, from GeeksForGeeks-how-to-save-data-to-the-firebase-realtime-database-in-android but for me the Data is not getting Added in the Database

I've used the Firebase Assistant in Android Studio

This is the MainActivity, It has only 2 buttons which go to the activities for adding Data and Viewing them

Java File for MainActivity:

package com.anurag.newemsapp;

import androidx.appcompat.app.AppCompatActivity;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    Button btnAdd, btnView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnAdd = findViewById(R.id.btnAdd);
        btnView = findViewById(R.id.btnView);

        btnAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Intent a = new Intent(MainActivity.this, AddActivity.class);
                startActivity(a);
            }
        });
        
      // the View button is disabled for time-being

    }
}

The Add Activity, This is where, I take user input and try to save the data in Firebase

Java File for AddActivity

package com.anurag.newemsapp;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.text.TextUtils;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

public class AddActivity extends AppCompatActivity {

    private EditText etAddEid, etAddEname;
    private Button btnAddSave;


    FirebaseDatabase firebaseDatabase;
    DatabaseReference databaseReference;

    Employee employee;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_add);

        etAddEid = findViewById(R.id.etAddEid);
        etAddEname = findViewById(R.id.etAddEname);

        firebaseDatabase = FirebaseDatabase.getInstance();

        databaseReference = firebaseDatabase.getReference("Employee");

        employee = new Employee();

        btnAddSave = findViewById(R.id.btnAddSave);

        btnAddSave.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                String id = etAddEid.getText().toString();
                String name = etAddEname.getText().toString();

                if (id.length() == 0 && name.length() == 0) {
                    Toast.makeText(AddActivity.this, "Please add some data.", Toast.LENGTH_SHORT).show();
                } else {
                    addDataToFirebase(id, name);
                }
            }
        });
    }

    private void addDataToFirebase(String id, String name) {
        employee.setEmployeeId(id);
        employee.setEmployeeName(name);
        databaseReference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                databaseReference.push().setValue(employee);
                Toast.makeText(AddActivity.this, "data added", Toast.LENGTH_SHORT).show();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Toast.makeText(AddActivity.this, "Fail to add data " + error, Toast.LENGTH_SHORT).show();
            }
        });
    }
}

Now When I press the Save Button, it does the validation part but, addDataToFirebase doesn't seem to work. I doesn't throw an error, the app runs perfectly fine. it's just the data that is not being added to Firebase Realtime Database

I have added the google-services.json file in the project level, after manually downloading it from the firebase console