Error making a post in the API with javascript

I'm trying to make a post in the API, using JSON, but it always returns page error not found. But I'm sure the URL is correct, because when I use "POSTMAN" it works perfectly.

Follow the javascript code.

var btncadastro = document.querySelector("#cadastrar");

btncadastro.addEventListener("click", function(event){
    event.preventDefault();
console.log("fui clicado");

var idnome      = document.querySelector("#nome");
var idra        = document.querySelector("#ra");
var idsenha     = document.querySelector("#senha");
var idemail     = document.querySelector("#email");

//Pega o status
var idstatus = document.select.status.selectedIndex;
var status_id = document.select.status[idstatus].value;

var nome = idnome.value;
var ra = idra.value;
var senha = idsenha.value;
var email = idemail.value;

var usuario = ({
    "ra"        : ra,
    "senha"     : senha,
    "nome"      : nome,
    "email"     : email,
    "status_id" : status_id
});

console.log(nome);
console.log(status);

if (nome == '' || ra == '' || senha == '' || email =='') {

    var labelerro = document.querySelector("#erro");

    labelerro.textContent = "Algum dos campos está em branco";

}

else{

    var xhr;

    if (window.XMLHttpRequest) {
        xhr = new XMLHttpRequest();
    } else if(window.ActiveXObject) {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    }

    var data = JSON.stringify(usuario);
    xhr.open("POST", "http://www.dev-android.hol.es/Api/novousuario", true);
    xhr.setRequestHeader("Content-Type", "application/json");
    xhr.send(data);

    xhr.onreadystatechange = function(){
        if(xhr.readyState == 4){
            console.log("Foi");
            if(xhr.status == 200){
                console.log("funcionou");
                console.log(xhr.responseText);
            }
            else{
                console.log("Erro no servidor");
                console.log(xhr.status);
            }
        }
        else{
            console.log("erro no servidor");
        }
    }
    }
});

follows the API code in PHP

$app->post('/novousuario','postUsuario');
    function postUsuario(){
        $request = \Slim\Slim::getInstance()->request();
        $usuario = json_decode($request->getBody());

        $sql = "INSERT INTO usuario (
                                    ra,
                                    senha,
                                    nome,
                                    email,
                                    status_id)
                            values (
                                    :ra,
                                    :senha,
                                    :nome,
                                    :email,
                                    :status_id) ";

        $conn = getConn();
        $stmt = $conn->prepare($sql);
        $stmt->bindParam("ra",$usuario->ra);
        $stmt->bindParam("senha",$usuario->senha);
        $stmt->bindParam("nome",$usuario->nome);
        $stmt->bindParam("email",$usuario->email);
        $stmt->bindParam("status_id",$usuario->status_id);
        $stmt->execute();
        $usuario->id = $conn->lastInsertId();
        echo json_encode($usuario);
    }

Can You Help Me?