Can not use Firesharp OnAsync

Question

I'm trying to detect the change in firebase realtime DB I'm using firesharp OnAsynce method, the error is 401: Unauthorized While I can use other method normally (like get, push, post, put) Thanks for help!

IFirebaseConfig firebaseConfig = new FirebaseConfig
{
    AuthSecret = "",
    BasePath = ""
};
FirebaseClient client = new FirebaseClient(firebaseConfig);
EventStreamResponse response = await client.OnAsync("Students/", (sender, args, context) =>
            {
                System.Console.WriteLine(args.Data);
            });