I don't know the flutter_local_notifications plugin but the doc says you have to ask for permission like this:

FlutterLocalNotificationsPlugin flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin(); flutterLocalNotificationsPlugin.resolvePlatformSpecificImplementation< AndroidFlutterLocalNotificationsPlugin>().requestNotificationsPermission();

The doc : https://pub.dev/packages/flutter_local_notifications#requesting-permissions-on-android-13-or-higher