Xamarin The remote server returned an error 401 unauthorized

[JeremyDeveloper]

Hello,
I'm facing a problem where I'm requesting data from the server and I'm receiving the following exception

System.Net.WebException: The remote server returned an error: (401) Unauthorized.

The code : 

var request = new OAuth2Request("GET", new Uri("https://api.fitbit.com/1/user/-/profile.json"), null, account);
var result = await request.GetResponseAsync();