Users' login details are lost after redirected from WorldPay

FormsAuthenticationTicket ticket = new FormsAuthenticationTicket

                (1, // Ticket version

                UserName, // Username associated with ticket

                DateTime.Now, // Date/time issued

                DateTime.Now.AddMinutes(30), // Date/time to expire

                false, // "true" for a persistent user cookie

                HttpContext.Current.Session["UserType"].ToString(), // User-data, in this case the roles

                FormsAuthentication.FormsCookiePath);

           
// add cookies

string hash = FormsAuthentication.Encrypt(ticket);

            HttpCookie cookie = new HttpCookie(

                        FormsAuthentication.FormsCookieName, // Name of auth cookie

                        hash); // Hashed ticket

            // Set the cookie's expiration time to the tickets expiration time

            if (ticket.IsPersistent) cookie.Expires = ticket.Expiration;

            // Add the cookie to the list for outgoing response

            HttpContext.Current.Response.Cookies.Add(cookie);