Unable to retrieve access token using MSAL for Android - azure

Question

I've been trying to integrate my Android Application with Azure AD B2C using MSAL but I can't figure out how to retrieve my access token using a custom scope. I'm using this MSAL samples as a reference.
I already granted my application the needed permissions but i still get this message:
No access is found for scopes: https://rbxsoftb2c.onmicrosoft.com/rbx/get_access_token
Here's my Azure B2C settings, MSAL Constants and the API I'm trying to access :
MSAL Constants :
public class Constants {
/* Azure AD b2c Configs */
final static String AUTHORITY = "https://login.microsoftonline.com/tfp/%s/%s";
final static String TENANT = "rbxsoftb2c.onmicrosoft.com";
final static String CLIENT_ID = "MY_CLIENT_ID";
final static String SCOPES = "https://rbxsoftb2c.onmicrosoft.com/rbx/get_access_token";
final static String API_URL = "https://rbxsoft.azurewebsites.net/api/values";
final static String SISU_POLICY = "B2C_1_SiUpIn";
final static String EDIT_PROFILE_POLICY = "B2C_1_edit_profile";
}
My API :
[Produces("application/json")]
[Route("api/Values")]
[Authorize]
public class ValuesController : Controller
{
CosmosDatabaseConnection cdc = CosmosDatabaseConnection.Instance;
// GET: api/Values
[HttpGet]
public JValue Get()
{
AppState appState = SessionManager.GetCookieSession(HttpContext.Session, User);
return new JValue ( appState.User.profile.ToString() );
}
}