If you have same problem like me,.. This is the solution ….
you should add clearfix div; after tag col-xs , you can’t click your form input because it is under the div col-md-12
this is sample code that you can use :

<form role="form">
<div class="row">
    <div class="col-xs-12">
        <div class="form-group">
            <label>Input XS</label>
            <input type="text">
        </div>
    </div>
    <div class="clearfix"></div>
    <div class="col-md-12">
        <div class="form-group">
            <label>Input MD</label>
            <input type="text">
        </div>
    </div>
</div>

Keep Smile and Happy Code… (●’◡’●)