Footer not working

var rid="3";
var yr="2024";
var mtg=0;
var mg=0;
var bsum=0;
var tableTN = $('#TdataTable').DataTable( {
  columnDefs: [{
              "className": "dt-center",
              "targets": "_all"
}],

         "ordering": false,
         "stateSave": true,
         "serverSide": false,
         "fixedHeader": true,
        "paging": true,
        "pageLength": 100,
        "lengthMenu": [[10, 25, 50,100, -1], [10, 25, 50,100, "All"]],

        "ajax": {
            'type': 'POST',
         'url':baseURL +'targetList',
         'data': {
       id: rid,
       year: yr
    },
         "dataSrc": function(json) {

// if (json.CustomVariable) {
// $("#some_span").html(json.CustomVariable);
// }
mtg=Math.round(json.target/12);
mg=mtg;
$('#exe').text(json.exe);
console.log(json.exe);
$('#yr').text(json.yr);
return json.data;
},
},
'columns': [
{ data: 'Clientname' },
{ data: 'JAN' },
{ data: 'FEB' },
{ data: 'MAR' },
{ data: 'APR' },
{ data: 'MAY' },
{ data: 'JUN' },
{ data: 'JUL' },
{ data: 'AUG' },
{ data: 'SEP' },
{ data: 'OCT' },
{ data: 'NOV' },
{ data: 'DEC' },
{ data: 'Total' }
],
"footerCallback": function(row, data, start, end, display) {
var api = this.api();
var secondaryFooterValues = []; // Array to store values for secondary footer
var thirdFooterValues = []; // Array to store values for secondary footer
secondaryFooterValues.push("Target");
thirdFooterValues.push("Achieved");
var sum=0;
api.columns('.sum', {
page: 'current'
}).every(function() {
sum = this
.data()
.reduce(function(a, b) {
var x = parseFloat(a) || 0;
var y = parseFloat(b) || 0;
return x + y;
}, 0);

$(this.footer()).html(sum);

bsum=mg-sum;
secondaryFooterValues.push(mg);

thirdFooterValues.push(Math.round(sum/mg*100)+"%");
mg=mtg+bsum;

});
secondaryFooterValues[13]=mtg12;
thirdFooterValues[13]=Math.round((sum/(mtg12))*100)+"%";

var secondaryFooter = $(api.table().footer()).find('.secondary-footer');
if (secondaryFooter.length === 0) {
secondaryFooter = $('<tr align="center" class="secondary-footer"></tr>').appendTo(api.table().footer());
}
secondaryFooter.empty(); // Clear existing content
secondaryFooterValues.forEach(function(value) {
$('<td>').html(value).appendTo(secondaryFooter);
});
var thirdFooter = $(api.table().footer()).find('.third-footer');
if (thirdFooter.length === 0) {
thirdFooter = $('<tr align="center" class="third-footer" style="font-size:16px;font-weight:bold;color:red"></tr>').appendTo(api.table().footer());
}
thirdFooter.empty(); // Clear existing content
thirdFooterValues.forEach(function(value) {
$('<td>').html(value).appendTo(thirdFooter);
});

},"fnRowCallback": function(nRow, aData, iDisplayIndex, iDisplayIndexFull) {
$('td', nRow).eq(0).css('color', 'blue');
},

    dom: '<"top"B>rt<"bottom"><"clear">',

    "buttons": [
   {
   extend: 'excelHtml5',
   exportOptions: {
     rows: function(idx, data, node) {
                  return true; // Export all rows
              },
       columns: [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
   }

},
{
extend: 'pdfHtml5',
exportOptions: {
columns: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
}
}
],

} );

//when i export as excel document footers does not add into document...assist with this..