Flutter – Login function returns NULL

I am implementing a login feature in flutter using Express. I have created a login API which works absolutely fine on Postman. When correct credentials are provided a token is generated and returned.

But when I use the same API in flutter, the token returns null.
The following is my authService.dart file :

// services/auth_service.dart
import 'dart:convert';
import 'package:http/http.dart' as http;
import 'package:manunited_trivia/models/User.dart';
import 'package:shared_preferences/shared_preferences.dart';

class AuthService {
  final String baseUrl =
      "http://192.168.1.6:8080/api/auth"; 

  Future<String?> register(String email, String password) async {
    try {
      final response = await http.post(
        Uri.parse('$baseUrl/register'),
        headers: {'Content-Type': 'application/json'},
        body: jsonEncode({'email': email, 'password': password}),
      );

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body);
        return data['token'];
      } else {
        return null;
      }
    } catch (e) {
      print('Error: $e');
      return null;
    }
  }

  Future<String?> login(String email, String password) async {
    try {
      final response = await http.post(
        Uri.parse('$baseUrl/login'),
        headers: {'Content-Type': 'application/json'},
        body: jsonEncode({'email': email, 'password': password}),
      );

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body);
        return data['token'];
      } else {
        return null;
      }
    } catch (e) {
      print('Error: $e');
      return null;
    }
  }

  Future<User?> getUser(String token) async {
    try {
      final response = await http.get(
        Uri.parse('$baseUrl/user'),
        headers: {
          'Content-Type': 'application/json',
          'x-auth-token': token,
        },
      );

      if (response.statusCode == 200) {
        final data = jsonDecode(response.body);
        return User.fromJson(data);
      } else {
        return null;
      }
    } catch (e) {
      print('Error: $e');
      return null;
    }
  }
}

And the following is my Login Page :

import 'package:firebase_auth/firebase_auth.dart';
import 'package:flutter/material.dart';
import 'package:manunited_trivia/constants/ColorsToUse.dart';
import 'package:manunited_trivia/screens/RegisterScreen.dart';
import 'package:manunited_trivia/services/auth_service.dart';
import 'package:quickalert/models/quickalert_type.dart';
import 'package:quickalert/widgets/quickalert_dialog.dart';
import 'package:shared_preferences/shared_preferences.dart';

class LoginScreen extends StatefulWidget {
  const LoginScreen({super.key});

  @override
  State<LoginScreen> createState() => _LoginScreenState();
}

class _LoginScreenState extends State<LoginScreen> {
  bool obscure = true;
  final TextEditingController _emailController = TextEditingController();
  final TextEditingController _passwordController = TextEditingController();

  final AuthService authService = AuthService();

  void _login(BuildContext context) async {
    String username = _emailController.text.trim();
    String password = _passwordController.text.trim();

    String? token = await authService.login(username, password);

    if (token != null) {
      // Store token in shared preferences for persistent login
      SharedPreferences prefs = await SharedPreferences.getInstance();
      prefs.setString('token', token);

      // Navigate to home screen
      Navigator.pushReplacementNamed(context, '/homeScreen');
    } else {
      print(token);
      // Handle login failure
      ScaffoldMessenger.of(context).showSnackBar(
        const SnackBar(content: Text('Login failed')),
      );
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      backgroundColor: Colors.white, // Background color
      body: Stack(
        children: <Widget>[
          Image.asset(
            'assets/images/header_bg.jpg', // Custom background image
            width: double.infinity,
            height: double.infinity,
            // opacity: const AlwaysStoppedAnimation(.85),

            fit: BoxFit.cover,
          ),
          Center(
            child: SingleChildScrollView(
              padding: const EdgeInsets.all(20.0),
              child: Column(
                mainAxisAlignment: MainAxisAlignment.center,
                crossAxisAlignment: CrossAxisAlignment.stretch,
                children: <Widget>[
                  Align(
                    alignment: Alignment.bottomCenter,
                    child: Text(
                      'Welcome to',
                      style: TextStyle(
                        fontFamily: "AldotheApache",
                        color: Colors.white,
                        fontSize: 24.0,
                        fontWeight: FontWeight.bold,
                        shadows: [
                          Shadow(
                            blurRadius: 5.0,
                            color: Colors.black.withOpacity(0.5),
                            offset: Offset(2.0, 2.0),
                          ),
                        ],
                      ),
                    ),
                  ),
                  const SizedBox(height: 10.0),
                  Text(
                    'The Theatre of Quiz',
                    style: TextStyle(
                      fontFamily: "AldotheApache",
                      color: ColorsToUse().unitedRed,
                      fontSize: 36.0,
                      fontWeight: FontWeight.bold,
                      letterSpacing: 2.0,
                      shadows: [
                        Shadow(
                          blurRadius: 5.0,
                          color: Colors.black.withOpacity(0.5),
                          offset: Offset(2.0, 2.0),
                        ),
                      ],
                    ),
                    textAlign: TextAlign.center,
                  ),
                  const SizedBox(height: 30.0),
                  TextField(
                    controller: _emailController,
                    decoration: InputDecoration(
                      filled: true,
                      fillColor: Colors.white.withOpacity(0.9),
                      hintText: 'Enter your email',
                      prefixIcon: const Icon(Icons.email),
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                    ),
                  ),
                  const SizedBox(height: 20.0),
                  TextField(
                    controller: _passwordController,
                    obscureText: obscure,
                    decoration: InputDecoration(
                      filled: true,
                      fillColor: Colors.white.withOpacity(0.9),
                      hintText: 'Enter your password',
                      prefixIcon: const Icon(Icons.lock),
                      suffixIcon: IconButton(
                          onPressed: () {
                            setState(() {
                              obscure = !obscure;
                            });
                          },
                          icon: const Icon(
                            Icons.remove_red_eye,
                            size: 20,
                          )),
                      border: OutlineInputBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                    ),
                  ),
                  const SizedBox(height: 20.0),
                  ElevatedButton(
                    onPressed: () {
                      _login(context);
                    },
                    style: ElevatedButton.styleFrom(
                      backgroundColor:
                          Colors.white, 
                      padding: const EdgeInsets.symmetric(vertical: 15.0),
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      shadowColor: Colors.black,
                      elevation: 5,
                    ),
                    child: const Text(
                      'Login',
                      style: TextStyle(fontSize: 18.0),
                    ),
                  ),
                  const SizedBox(
                    height: 20,
                  ),
                  ElevatedButton(
                    onPressed: () {
                      Navigator.of(context).push(MaterialPageRoute(
                          builder: (context) => RegisterScreen()));
                    },
                    style: ElevatedButton.styleFrom(
                      backgroundColor:
                          Colors.white, // Manchester United's primary color
                      padding: const EdgeInsets.symmetric(vertical: 15.0),
                      shape: RoundedRectangleBorder(
                        borderRadius: BorderRadius.circular(10.0),
                      ),
                      shadowColor: Colors.black,
                      elevation: 5,
                    ),
                    child: const Text(
                      'Register',
                      style: TextStyle(fontSize: 18.0),
                    ),
                  ),
                ],
              ),
            ),
          ),
        ],
      ),
    );
  }
}

This line String? token = await authService.login(username, password); return null for some reason.
Can anyone help?

I was expecting the token to returned after calling the api in the authService file.