Can't click anything after i open my Bootstrap modal

Question

sorry for the basic question, I'm working on MVC ASP.NET and I'm trying to add a bootstrap modal in my navbar, I run the code, i can see the button i can touch on it, but after it open, the screen is unclickable i have to f5 to click anywhere again, it's the first time i use modals from bootstrap, and search all around google if I have to write some JavaScript code, but everywhere says that you just need jquery , bootstrap.js and .css and nothing else. If I'm missing something just let me know. Thanks, Here is my code.

PD: I have a carousel already working from bootstrap

@if (Session["usuario"] == null)
            {
                <button type="button" class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
                    Ingresar
                </button>

                <!-- Modal -->
                <div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel">
                    <div class="modal-dialog" role="document">
                        <div class="modal-content">
                            <div class="modal-header">
                                <button type="button" class="close" data-dismiss="modal" aria-label="Close"><span aria-hidden="true">&times;</span></button>
                                <h4 class="modal-title" id="myModalLabel">Iniciar Sesión</h4>
                            </div>
                            <div class="modal-body">
                                <form method="post" action="@Url.Action("DoLogin","Usuario")">
                                        <span class="alert-danger">@ViewBag.NoUser</span>
                                        <label for="NombreDeUsuario" class="sr-only">Nombre de Usuario</label>
                                        <input type="text" id="NombreDeUsuario" name="NombreDeUsuario" class="form-control" placeholder="Ingresa tu Usuario" required="" autofocus="" />
                                        <br />

                                        <label for="Contrasena" class="sr-only">Contraseña</label>
                                        <input type="password" id="Contrasena" name="Contrasena" class="form-control" placeholder="Ingresa tu Contraseña" required="" />
                                        <br />
                                        <button class="btn btn-lg btn-primary btn-block" type="submit">Ingresar</button>
                                 </form>
                            </div>
                            <div class="modal-footer">
                                <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
                            </div>
                        </div>
                    </div>
                </div>
            }

Here is a screenshot of the problem

Answer 1

.modal-backdrop {
  z-index: -1;
}

Answer 2

Try this:

$(document).off('focusin.modal');

Its just because the modal is focused.