jQuery DataTable - "Processing" does not appear

I am having problem displaying the processing message in a jQuery data table. I looked around for this issue and followed all suggestions to no avail. Only one suggestion works but partially.

I tried:

var tblFacCert = $("#tblFacCert").on('processing.dt', function (e, settings, processing) {
    if (processing) {
        if ($('#imgLoad').length == 0)
            $(this).prepend('<img id="imgLoad" src="../assets/images/PleaseWait.gif" alt="" />');
    }
    else
        $('#imgLoad').remove();
}).DataTable({
    dom: 'lfrtip',
    processing: true,
    ....
}),

Also:

<style type="text/css">
    #tblFacCert_processing {
        top: 64px !important;
        z-index: 11000 !important;
        visibility:visible;
        background-image:url("../assets/images/PleaseWait.gif"); background-repeat:no-repeat;
    }
</style>

This partially works. It shows the the word "Processing ..." but won't go away when table is populated. Also, it shows up on page postback, like making a selection in a drop down list, presumably because I am redrawing on postback.

"preDrawCallback": function () {
    $('.dataTables_processing').attr('style', padding-bottom: 60px; display: block; z-index: 10000 !important');
},

Update - after adding serverSide:true

I had initially added "serverSide: true" to data table definition but removed it after getting this error: "Unhandled exception at line 36, column 442 in https://cdn.datatables.net/1.10.16/js/jquery.dataTables.min.js 0x800a138f - JavaScript runtime error: Unable to set property 'data' of undefined or null reference".

I have two data tables on the page, they get populated when a "Submit" button is clicked. This is how I am setting up and populating them (I am including one data table only for brevity)

var tblFacCert = $("#tblFacCert").DataTable({
    jQueryUI: true,
    "serverSide": true, // This causes error
    data: [],
    dom: 'lfrtip',
    processing: true,
    stateSave: true,
    "lengthMenu": [[15, 25, 50, -1], [15, 25, 50, "All"]],
    order: [[0, "asc"], [1, "asc"], [2, "asc"], [3, "asc"]],

    "columns": [
        {
            "data": "Area"
        }, {
            "data": "District"
        }, { ... more columns ...}
    ],
    "columnDefs": [ ...
    ],
    "pageLength": 15,
    deferRender: true,
    scrollCollapse: true,
    scroller: true,
    "preDrawCallback": function () {
        $('#tblFacCert_processing').attr('style', 'padding-bottom: 60px; display: block; z-index: 10000 !important');
    },
    "rowCallback": function (row, data, index) {
        ...
    }
});

// Get data for both data tables and populate
$("#btnSubmit").on("click", function (event) {
    var facCertUrl = "../services/easg.asmx/GetComplianceReportData";
    var facCertParams = "{ 'startDate': '" + $("#tbStartDate").val() + "', 'certID': '" + $('#ddlCertificate').val() + "'}";
    var statsUrl = "../services/easg.asmx/GetFacComplianceByArea";
    var statsParams = "{ 'startDate': '" + $("#tbStartDate").val() + "', 'certID': '" + $('#ddlCertificate').val() + "'}";
    populteTable(statsUrl, statsParams, tblStats);
    populteTable(facCertUrl, facCertParams, tblFacCert);
})

function populteTable(ws_url, parameters, table) {
    $.ajax({
        type: "POST",
        dataType: "json",
        contentType: "application/json; charset=utf-8",
        url: ws_url,
        cache: false,
        data: parameters,
    }).done(function (result) {
        table.clear().draw();
        table.processing = true;
        jResult = JSON.parse(result.d);
        table.rows.add(jResult).draw();
    }).fail(function (jqXHR, textStatus, errorThrown) {
        alert(textStatus + ' - ' + errorThrown);
    });
}

The processing message would only be displayed if you've got server-side processing enabled. In the example here, you'll see it flick up briefly, but only briefly as the dataset is small the processing takes little time.

    var dt = $('#example').DataTable( {
    "processing": true,
    "serverSide": true,
    "ajax": "/ssp/objects.php",
    "columns": [
        { "data": "first_name" },
        { "data": "last_name" },
        { "data": "position" },
        { "data": "office" },
        { "data": "start_date" },
        { "data": "salary" }
    ]
} ); 

If this doesn't resolve it for you, and it doesn't display the processing message, it would be worth pasting your entire table initialisation code.