i am trying to run a autocomplete function and get the data however i am end up getting an error that is "internal server error 500"

my client side code is the below please help

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js">
</script>

<script src="../Scripts/jquery-ui.js"></script>
<link href="../Scripts/jquery-ui.css" rel="stylesheet" />
<script type="text/javascript">
    $(document).ready(function () {
        debugger;
        $("#txtautocomplete").autocomplete({
            source: function (request, response) {
                debugger;
                var txtname = $("#txtautocomplete").val();
                alert(txtname);

                $.ajax({
                    url: "../EmployeeService.asmx/GetAllEmpBYName",
                    method: "post",
                    data: JSON.stringify({ term: txtname }),
                    ContentType: "application/json;charset-utf-8",
                    dataType: "json",
                    success: function (data) {
                        response(data.d);
                    }, error: function (err) {
                        // alert(err.error);\

                        alert(err);

                    }
                });
            }

        });