Invalid length for a Base-64 char array or string.

WhatsApp wz = new WhatsApp(s, "dskgjhgkjgkjgg=", "RTS", false, false);
wz.OnConnectSuccess += () =>
{
     MessageBox.Show("conected to whatsup");
     wz.OnLoginSuccess += (phonenNumber, data) =>
     {
           wz.SendMessage(to, msg);
           MessageBox.Show("mesageSent");
     };
                    
     wz.OnLoginFailed += (data) =>
     {
           // wz.SendMessage(to, msg);
           MessageBox.Show("Login Failed :{0}",data);
     };
              
     wz.Login();
     // error is here(Invalid length for a Base-64 char array or string)
                };