Flutter didChangeAppLifecycleState is not working

Unsure about the setup of your application but I can provide you with the base code that works on my end.

First, create a lifecylce_manager.dart file which includes:

class LifeCycleManager extends StatefulWidget {
final Widget child;
const LifeCycleManager({super.key, required this.child});

@override
LifeCycleManagerState createState() => LifeCycleManagerState();
}

class LifeCycleManagerState extends State<LifeCycleManager>
  with WidgetsBindingObserver {

@override
void initState() {
 WidgetsBinding.instance.addObserver(this);
 super.initState();
}

@override
void dispose() {
  WidgetsBinding.instance.removeObserver(this);
  super.dispose();
}

@override
void didChangeAppLifecycleState(AppLifecycleState state) {
  // TODO: implement didChangeAppLifecycleState
  UpPrint(name: "CheckUserStatus", value: "Before");
  print(state);
  UpPrint(name: "CheckUserStatus", value: "After");
  if (state == AppLifecycleState.resumed) {
    //TODO: set status to online here in firestore
    UpPrint(name: "CheckUserStatus", value: "Online");
    UpFirebaseDB.updateUserStatus(status: true);
  } else {
    //TODO: set status to offline here in firestore
    UpFirebaseDB.updateUserStatus(status: false);
    UpPrint(name: "CheckUserStatus", value: "Offline");
  }
}
@override
Widget build(BuildContext context) {
  return Container(
    child: widget.child,
  );
 }
}

Then, in the main.dart file or your applications entry point:

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
const MyApp({super.key});

@override
Widget build(BuildContext context) {
  return LifeCycleManager(
    child: MaterialApp(
      initialRoute: '/',
      onGenerateRoute: UpRoutes.onGenerateRoute,
      theme: appTheme(),
    ),
  );
 }
}