Search by Colum

Hi,

I want to enable inputbox to search for some columns, i enable search on columns but didn't work, any help ?

HTML Code:

        <nav class="navbar navbar-inverse navbar-fixed-top">
            <div class="container">
                <div class="navbar-header">
                    <button type="button" class="navbar-toggle" data-toggle="collapse" data-target=".navbar-collapse">
                        <span class="sr-only">Toggle navigation</span>
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                        <span class="icon-bar"></span>
                    </button>
                    <a class="navbar-brand" href="/">websample</a>
                </div>
                <div class="navbar-collapse collapse">
                    <ul class="nav navbar-nav">
                        <li><a href="/">Home</a></li>
                        <li><a href="/Home/About">About</a></li>
                        <li><a href="/Home/Contact">Contact</a></li>
                    </ul>
                </div>
            </div>
        </nav>
        <div class="container body-content">

            <h2>Index</h2>
            <table class="table table-bordered " id="PeopleListTable"></table>


            <hr />
            <footer>
                <p>&copy; 2017 - websample</p>
            </footer>
        </div>

Javascript Code

<script type="text/javascript">
        $(function () {
            var peopleList = $('#PeopleListTable').DataTable({
                serverSide: true,
                processing: true,
                searching: true,
                stateSave:true, 

                ajax: {
                    url: '/Teste/Data',
                    type: "POST"
                },
                columns: [
                    { data: "FirstName", title: "First Name",searchable:true, orderable: false },
                    { data: "LastName", title: "Last Name" },
                    { data: "BirthDateFormatted", title: "Birth Date", orderData: 3 }, //Allow post TSQL server side processing
                    { data: "BirthDate", visible: false },
                    { data: "Weight", title: "Weight" },
                    { data: "Height", title: "Height" },
                    { data: "Children", title: "Children" }

                ]
            });
        });
    </script>

However i enable searchable but not appearing any inputbox. Why not ?