StooqImporter not work

[uranio-235]

System.AggregateException
  HResult=0x80131500
  Mensaje = One or more errors occurred.
  Origen = System.Private.CoreLib
  Seguimiento de la pila:
   at System.Threading.Tasks.Task`1.GetResultCore(Boolean waitCompletionNotification)
   at playground.Program.Main(String[] args) in C:\Users\lazaro\source\repos\trading\playground\Program.cs:line 21

Excepción interna 1:
Exception: No data

Code simple

var grafico = new StooqImporter()
   .ImportAsync("FB", DateTime.Now - TimeSpan.FromDays(60)).Result;

[uranio-235]

my bad. Stooq symbols should be FB.US

any way, it return an empty dataset