non-local notification using workManager flutter - flutter

Question

i tried to send notification to another device when the app is terminated using workManager
it does not work, however the same function works if i use it without workManager
here is the code
in the main
await Workmanager().initialize(callBAckDispatcher, isInDebugMode: true);
callBackDispathcer
callBAckDispatcher() {
WidgetsFlutterBinding.ensureInitialized();
Firebase.initializeApp();
Workmanager().executeTask((taskName, inputData) async {
if (taskName == "t") {
int id = 7
await sFunction(id, await returnUserName());
}
return Future.value(true);
});
}
sFunction
sFunction(int id, String sender) async {
List<Map> response =
await SQLdb().readData('''SELECT * FROM `timer_chat` WHERE id = $id
''');
String reciever = response[0]['reciever'];
String message = response[0]['message'];
try {
String currentToken = await auth.getusertoken(reciever);
auth.sendnotify("my app",
"your message has been sent: " + message, "1", currentToken);
} catch (e) {
print("notification did not send: " + e.toString());
}
}
finally sendnotify
sendnotify(String title, String body, String id, String token) async {
try {
await http.post(
Uri.parse("https://fcm.googleapis.com/fcm/send"),
headers: <String, String>{
'content-type': 'application/json',
'Authorization': 'key=$serverToken',
},
body: jsonEncode(
<String, dynamic>{
'notification': <String, dynamic>{
'body': body.toString(),
'title': title.toString()
},
'priority': 'high',
'data': <String, dynamic>{
'click_action': "FLUTTER_NOTIFICATION_CLICK",
'id': id.toString(),
"name": "me",
"lastname": "wolf"
},
"to": token
},
),
);
} catch (e) {
print("something went wrong in notiiiii" + e.toString());
}
}
i'm sending notifications using firebase cloud messaging API. it worked fine inside the app but in workManager it does not. any idea why?
thank you