next button does not work when using pagination

hello everyone, i have a problem on using dataTables 1.9 and i need you guys help me with this.

i set the pagination style to "full numbers", the [next] button does not work when i use pagination,
but the [Previous] button and page number button works perfectly.

anyone know what the reason for this.
thank you!

javascript :

$(document).ready(function() {
  $('#example').dataTable({
    "bPaginate": true,
        "sPaginationType": "full_numbers",
        "bFilter": true,
        "bSort": true,
        "bInfo": false,
        "bJQueryUI": true,
        "bLengthChange": true,
        "sScrollX": "50%",
        "bStateSave": true,
        "bProcessing": true,
        "bServerSide": true,
        "sAjaxSource": ".../supporttool/new_queue/query_ajax",
        "fnServerParams": function ( aoData ) {
            var app_id = $('#app_id').val();
            var request_start_date = $('#request_start_date').val();
            var request_end_date = $('#request_end_date').val();
            if(app_id){
                aoData.push( {"name": "app_id","value": app_id});
            }
            if(request_start_date){
                aoData.push( {"name": "request_start_date","value": request_start_date});
            }
            if(request_end_date){
                aoData.push( {"name": "request_end_date","value": request_end_date});
            }
        },
        "bDeferRender": true,
        "bAutoWidth": true
          });
} );

the response json is like:

{
    "sEcho":2,
    "iTotalRecords":"5683",
    "iDisplayLength":10,
    "aaData":[
        ...
    ]
}