Calling Ajax with multiple array but not getting function call

I am calling Ajax with multiple array but not getting function call on click of ctl00_MainContent_btnsaveqfdmatrix i am passing array custreq ,testpara ,category,property1 value in ajax call

$('#ctl00_MainContent_btnsaveqfdmatrix').click(function(e) {
      e.preventDefault();
      var custreq = [];
      var testpara = [];
      var category = [];
      var property1 = [];
      $("#Qfd td").each(function() {
            if ($(this).hasClass("highlight1")) {
              alert("check1");
              cols = $(this).closest("tr").children("td").index($(this));
              custreq[i++] = $(this).closest("tr").find("td").eq(0).html(); //colv
              if ($(this).closest("tr").find("td").eq(1).hasClass("A")) {
                custreq[i++] = $(this).closest("tr").find("td").eq(1).html(); //colv
              } else {
                cols = 1 + cols
              }
              testpara[i++] = $("#Qfd tr").eq(1).find("td").eq(cols).html(); //rowv
              if (cols <= 6 && cols >= 1) {
                category[i++] = 'Alloying';
              }
              if ($(this).hasClass("highlight1")) {
                property1[i++] = "Red"
              }
              $.ajax({
                type: "POST",
                url: "Entry.aspx/mcall",
                data: {
                  'custreq': custreq,
                  'testpara': testpara,
                  'category': category,
                  'property1': property1,
                  'npdno': $("#ctl00_MainContent_lblnpdno").text()
                },
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function(data) {
                  alert("yes");
                },
                error: function(response) {
                  alert(response);
                }
              });
            });

in vb .net side calling webmethod mcall but given function is not able to call

<ScriptMethod(),
    WebMethod()>
Public Shared Function mcall(ByVal custreq As List(Of String), ByVal testpara As List(Of String), ByVal category As List(Of String), ByVal property1 As List(Of String), ByVal npdno As String) As String

  Return "Hello "
    End Function

Any idea where is error will be appreciated.