check internet connection not remove pop-up flutter

Question

I'm trying to insert a listener in my app that always checks the connection, both when I'm with the app open and when it's in the background. with transition from wifi to 3g too.

I am using the connectivity_plus library and I am declaring a listener in the iniot and in the dispose I delete the pop-up, I do not understand why I still have cases in which the pop-up does not work well. for example, if I am with wifi and 3G active, I go to the background I deactivate the wifi, if I enter the app it gives me the pop-up that I am not connected to the internet.

I don't understand where I'm wrong

    class ConnectivityStatus {
  factory ConnectivityStatus() => _instance;
  ConnectivityStatus._() {
    _init();
  }
  static final ConnectivityStatus _instance = ConnectivityStatus._();
 
  FlashController? _flashController;
 
  StreamSubscription? _lastSub;
 
  void _checkInternetConnectivity(ConnectivityResult status) {
    Future.delayed(const Duration(milliseconds: 50), () {
      if ([
        ConnectivityResult.mobile,
        ConnectivityResult.wifi,
      ].contains(status)) {
        // I am connected to a mobile network.
        if (_flashController != null) _flashController!.dismiss();
        _flashController = null;
      } else {
        logger.w('[Provider-checkInternetConnectivity] Missing connectivity');
 
        showFlash(
          context: Get.context!,
          onWillPop: () async => false,
          persistent: true,
          builder: (context, controller) {
            _flashController = controller;
            return Flash(
              controller: controller,
              position: FlashPosition.top,
              behavior: FlashBehavior.fixed,
              useSafeArea: true,
              backgroundColor: AppColors().red,
              barrierDismissible: false,
              enableVerticalDrag: false,
              child: FlashBar(
                content: localizations.checkInternet.rich(
                  style: const TextStyle(color: Colors.white),
                ),
                icon: Padding(
                  padding: const EdgeInsets.symmetric(horizontal: 15),
                  child: SvgPicture.asset(
                    'assets/svg/noWifi_white.svg',
                    height: 24,
                    width: 24,
                  ),
                ),
              ),
            );
          },
        );
      }
    });
  }
 
  void _onStatusChange(AppLifecycleState state) {
    logger.i('[Connectivity-status] State changed: $state');
    if (state == AppLifecycleState.inactive ||
        state == AppLifecycleState.paused ||
        state == AppLifecycleState.resumed ||
        state == AppLifecycleState.detached) {
      _lastSub?.cancel();
      _lastSub = Connectivity()
          .onConnectivityChanged
          .listen(_checkInternetConnectivity);
    }
  }
 
  void _init() {
    if (_flashController != null) _flashController?.dismiss();
 
    StreamGroup.merge([
      Future.value(AppLifecycleState.resumed).asStream(),
      AppStatus().lifecycleStream
    ]).listen(_onStatusChange);
  }
 
  @protected
  void dispose() {
    if (_lastSub != null) _lastSub?.cancel();
    if (_flashController != null) _flashController?.dismiss();
  }
}