I'm loading table through ajax.

    $('#sample_1').dataTable( {
        "bProcessing": true,
        "bServerSide": true,
        "sAjaxSource": baseUrl+"/admin/employee/getusers/type/admin/group/"+groupdata ,
        "aaSorting": [[ 0, "desc" ]],
        "bInfo":false,
        "aoColumnDefs": 
         [
            { "bSortable": false, "aTargets": [1,2,4,5,6,7,8] },
            
         ],
        "iDisplayLength":50,
        "aLengthMenu": [[50, 100, 500, -1], [50, 100, 500, "All"]],
        "fnDrawCallback": function( oSettings ) {
            re_init();
        },
            "language": {
            "lengthMenu": "_MENU_ "+records,
            "sZeroRecords": zerorecord,
            "sSearch":searchv+":",
            "sProcessing":processing+"...",
            "sLoadingRecords":loading+"...",
            "sEmptyTable":emptytable,
            
        },
}

Now I wanted to add button to export some data into excel file, so after the "language" I added

        dom: 'Blfrtip',
        buttons: [
            {
                extend: 'excelHtml5',
                title: 'Report',
                text:"Export",
                exportOptions: {
                    columns: [1,2,3,4,5,6,7,8,9]
                }
            },
        ]

The table shows up. There are no errors, but the button is nowhere to be found. I have very similar export with different table on different site that works perfectly fine.

    $('#sample_1').dataTable( {
        "bProcessing": true,
        "bServerSide": true,
        "bInfo":false,
        "aoColumnDefs": 
         [
            { "bSortable": false, "aTargets": [10] },
            { "bSearchable": false, "aTargets": [0,4,5,6,7,8,9,10] /*Not To include*/ }             
         ],
        "sAjaxSource": baseUrl+"/admin/lectures/getresults",
        "iDisplayLength":50,
        "aLengthMenu": [[50, 100, 500, -1], [50, 100, 500, alls]],
        "fnServerParams": function ( aoData ) {
            if(rl==1){
                aoData.push( {"name":"lectid","value":lectid},{"name":"b_group","value":b_group},{"name":"rl","value":1});
            }else{
                aoData.push( {"name":"lectid","value":lectid},{"name":"b_group","value":b_group});//
            }
        },
        "fnDrawCallback": function( oSettings ) {
            //re_init();
        },
        "language": {
            "lengthMenu": "_MENU_ "+records,
            "sZeroRecords": zerorecord,
            "sSearch":searchv+":",
            "sProcessing":processing+"...",
            "sLoadingRecords":loading+"...",
            "sEmptyTable":emptytable,
        },
        dom: 'Blfrtip',
        buttons: [
            {
                extend: 'excelHtml5',
                title: 'Report',
                text:exportvar,
                exportOptions: {
                    columns: [1,2,3,4,5,6,7,8,9]
                }
            },
        ]
    } );

I didn't write that code originally, but now I'm stuck with it and I'm kind of lost.
Do you have any ideas?