Flutter web shows a blank screen in build mode

After finishing my web app on flutter I tried to release it on the server by flutter build web command. I uploaded my files to the server but I am getting a blank screen. In the debugging mode on Android Studio, it works fine. I am also getting the same blank screen when I use the command flutter run -d chrome --profile --verbose I found similar questions here but the root cause seems to be different every time and nothing worked for me, can you please advice?

Below is a simplified version of my flutter code, suffering from the same issue:

import 'dart:ui';
import 'package:flutter/material.dart';
import 'package:flutter/cupertino.dart';
import 'package:google_fonts/google_fonts.dart';
import 'package:flutter_signin_button/flutter_signin_button.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  //await Firebase.initializeApp();
  ErrorWidget.builder = (FlutterErrorDetails details) {
    bool inDebug = false;
    assert(() { inDebug = true; return true; }());
    // In debug mode, use the normal error widget which shows
    // the error message:
    if (inDebug)
      return ErrorWidget(details.exception);
    // In release builds, show a yellow-on-blue message instead:
    return Container(
      alignment: Alignment.center,
      child: Text(
        'Error! ${details.exception}',
        style: TextStyle(color: Colors.yellow),
        textDirection: TextDirection.ltr,
      ),
    );
  };
  // Here we would normally runApp() the root widget, but to demonstrate
  // the error handling we artificially fail:
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
          scrollBehavior: MyCustomScrollBehavior(), //fixing the scrolling for web
          home:LoginScreen(),


          theme: ThemeData(
            cupertinoOverrideTheme: CupertinoThemeData( // <---------- this
              textTheme: CupertinoTextThemeData(
                pickerTextStyle: TextStyle(color: Colors.white, fontWeight: FontWeight.w900),
              ),
            ),

          ),
        );

//
  }
}
class MyCustomScrollBehavior extends MaterialScrollBehavior {
  // Override behavior methods and getters like dragDevices
  @override
  Set<PointerDeviceKind> get dragDevices => {
    PointerDeviceKind.touch,
    PointerDeviceKind.mouse,
    // etc.
  };
}
class LoginScreen extends StatefulWidget {

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

}

class _LoginScreenState extends State<LoginScreen> {
  late String em;
  late String pa;
  @override
  void initState() {
    // TODO: implement initState
    super.initState();

  }
  @override
  Widget build(BuildContext context) {
    return Material(
        child: Scaffold(
              body: buildHomeScreen()
          ),
        );
  }

  Widget buildHomeScreen(){
   return Container(
      decoration: BoxDecoration(color: Colors.amberAccent),
      child: Flexible(
        child: SingleChildScrollView(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            crossAxisAlignment: CrossAxisAlignment.center,
            children: <Widget>[
              Align(alignment: Alignment.centerLeft,
                  child: WelcomeText('Get to know the highest rated cars,')),
              Align(alignment: Alignment.centerLeft,child: WelcomeText('good and bad things for each car,')),
              Align(alignment: Alignment.centerLeft,child: WelcomeText('best car mechanics near you,')),
              Align(alignment: Alignment.centerLeft,child: WelcomeText('best car agencies,')),
              Align(alignment: Alignment.centerLeft,child: WelcomeText('and more..')),
              SizedBox(height: 100,),
              Text('Welcome to Car of your Dreams', style: GoogleFonts.ubuntu(
                  textStyle: TextStyle(fontSize: 35,
                      color: Colors.white,
                      fontWeight: FontWeight.w500,
                      decoration: TextDecoration.none))),
              SizedBox(height: 8,),
              Text('Sign in to continue', style: GoogleFonts.ubuntu(
                  textStyle: TextStyle(fontSize: 14,
                      color: Colors.white,
                      fontWeight: FontWeight.w300,
                      decoration: TextDecoration.none))),
              SizedBox(height: 12,),
              FractionallySizedBox(
                widthFactor: 0.6,
                child: TextField(
                  onChanged: (value){
                  }
                  ,
                  decoration: InputDecoration(
                    hintText: "Email",
                    border: OutlineInputBorder(),
                    icon:Icon(Icons.email),
                    contentPadding: EdgeInsets.symmetric(horizontal: 20),
                  ),
                ),
              ),
              SizedBox(height: 5,),
              FractionallySizedBox(
                  widthFactor: 0.6,
                  child: TextField(
                      obscureText:true ,
                      onChanged: (value){
                      },
                      decoration: InputDecoration(
                        hintText: "Password",

                        border: OutlineInputBorder(),
                        icon:Icon(Icons.vpn_key_outlined),
                        contentPadding: EdgeInsets.symmetric(horizontal: 20),))
              ),
              SizedBox(height: 10,),
              Row(
                mainAxisAlignment: MainAxisAlignment.center,
                children: [
                  TextButton(onPressed: () {},
                    child: Text('Sign in', style: GoogleFonts.londrinaSolid(
                        textStyle: TextStyle(fontSize: 25,
                            color: Colors.white,
                            fontWeight: FontWeight.w300,
                            decoration: TextDecoration.none))),),
                  SizedBox(width: 10,),
                  Icon(Icons.arrow_forward, color: Colors.white,)
                ],
              ),
              SizedBox(height: 10,),
              SignInButton(Buttons.Google,
                  text: "Sign in with Google",
                  onPressed:(){}),
              SizedBox(height: 7,),
              SignInButton(Buttons.Facebook,
                  text: "Sign in with Facebook",
                  onPressed: (){}),
              SizedBox(height: 7,),
              TextButton(
                onPressed: (){
                  Navigator.pushNamed(context, '-1');
                },
                child: Text('New user? Register..', style: GoogleFonts.londrinaSolid(
                    textStyle: TextStyle(fontSize: 20,
                        color: Colors.white,
                        fontWeight: FontWeight.w300,
                        decoration: TextDecoration.none))),),
              SizedBox(height: 50,),

            ],
          ),
        ),
      ),
    );
  }

}

class WelcomeText extends StatelessWidget {
  WelcomeText(this.welcomeText) ;
  String welcomeText;
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.fromLTRB(20.0,0,0,0),
      child: Text(welcomeText,
          style: GoogleFonts.permanentMarker(
              textStyle: TextStyle(fontSize: 30,
                  color: Colors.white70,
                  fontWeight: FontWeight.w100,
                  decoration: TextDecoration.none))),
    );
  }
//'Get to know the highest rated cars, good and bad things for each car, best car mechanics near you, best car agencies and more...'
}