Buttons with specific class is not displayed

I use datatable with buttons plugings and bootstrap style.

With this code

    var url = '/i18n/' + '[(${#authentication.getPrincipal().getLang()})]' + '.json';
    var productTypesTable = $('#productTypesTable').DataTable({
                            responsive: {
                                details: {
                                    display: $.fn.dataTable.Responsive.display.childRowImmediate,
                                    type: ''
                                }
                            },
                            "language": {
                                "url" :  url
                            },
                            dom: 'Bfrtip',
                            buttons: {
                                dom: {
                                  button: {
                                    tag: 'button',
                                    className: ''
                                  }
                                },
                                buttons: [
                                    {
                                        extend: 'copy',
                                        className: 'btn btn-primary',
                                        text: '[(#{productType.new})]', //should come from thymeleaf
                                        action: function ( e, dt, node, config ) {
                                             $("#productTypesFragment").load("/template/new/producttypes");
                                        }
                                    }
                                ]
                            },
                            "bLengthChange": false, //hide 'show entries dropdown
                            'pagingType': 'simple_numbers'
                        });

Buttons is not displayed