DELETE FROM login_attempts WHERE ip = '$ip'"

echo 'username: '.$username.' / DB: '.$UsernamaDB;
echo 'password: '.$password.' / DB: '.$passwordDB;

<?php
  session_start();
  $message="";
  $captcha = true;

  $con =  @new mysqli('localhost', 'root', '', 'system');

  if(count($_POST)>0 && isset($_POST["vcode"]) && $_POST["vcode"]!=$_SESSION["vcode"]) {
    $captcha = false;
    $message = "Los caracteres escritos no coinciden con la palabra de verificación. Inténtalo de nuevo.";
  }

  $ip = $_SERVER['REMOTE_ADDR'];

  //Bloqueamos la ip por un día
  $result = mysqli_query($con,"SELECT * FROM failed_login WHERE ip='$ip' AND date BETWEEN DATE_SUB( NOW() , INTERVAL 1 DAY ) AND NOW()");
  $row  = mysqli_fetch_assoc($result);
  //Obtenemos datos para comprar intentos y para resetear intentos por su ultimo fecha.
  $failed_login_attempt = mysqli_real_escape_string($con,$row['attempts']);
  //Liberamos memoria.
  mysqli_free_result($result);

  if(count($_POST)>0 && $captcha == true) {
    $username = mysqli_real_escape_string($con, $_POST["username"]);
    $password = mysqli_real_escape_string($con, $_POST["password"]);
    $username = htmlentities($username);
    $password = htmlentities($password);
    $save_passw = sha1($password);
    $sql = "SELECT * fROM users where username='$username' AND password='$save_passw' AND active='1' ";
    $query = mysqli_query($con, $sql);

    $rowU  = mysqli_fetch_assoc($query);
    $UsernamaDB = mysqli_real_escape_string($con, $rowU["username"]);
    $passwordDB = mysqli_real_escape_string($con, $rowU["password"]);

    if($failed_login_attempt <1) {
            //Si es su primer intento fallido, incluimos el primer registro en la BD
            $con->query("INSERT INTO failed_login (ip,attempts,date) VALUES ('$ip', 1, NOW())");
            } else {
                if($failed_login_attempt <2){
                //En caso de ya estar en la BD, sacamos el valor y agregamos +1
                $contador = $row['attempts'] + 1;
                $con->query("UPDATE failed_login SET attempts='$contador', date=NOW() WHERE ip = '$ip'");
            }
        }


        if (empty($_POST) === false) {
            $username = $_POST['username']; $password = $_POST['password'];
            if (empty($username) === true || empty($password) === true) {
                $message = "Es necesario introducir un nombre de usuario y contraseña";
             } elseif ($username != $UsernamaDB) {
                $message = "El 'Usuario' que has introducido no coincide. ";
             } elseif ($save_passw != $passwordDB) {
                $message = "Tu 'Contraseña' introducido no coincide. ";
             } elseif($save_passw == $passwordDB && $username == $UsernamaDB) {
                $_SESSION["id_user"];
                $con->query("DELETE FROM login_attempts WHERE ip = '$ip'");
             }
            }
        }
        if(isset($_SESSION["id_user"])) {
            header("Location:http://localhost/learncode/index.php");
        }
?>
<?php include 'themes/template/header.php'; ?>
<div id="login" class="center">
  <div class="container">
    <div class="access">
        <h2>ENTRE AQUÍ.</h2>
        <h1><?php if($message!="") { echo $message; } ?></h1>
        <form name="frmUser" action="#" method="post">
            <input class="form-one" type="text" name="username" placeholder="username">
            <input class="form-one" type="password" name="password" placeholder="Password">
            <?php if (isset($failed_login_attempt) && $failed_login_attempt >= 1) { ?>
            <br><img src="image.php" id="phoca-captcha"/>
            <input name="vcode" type="text" placeholder="Codigo captcha">
            <?php } ?>
            <ul class="recovery">
              <li>
                  <input class="checkbox-one" type="checkbox" id="brand1" value="">
                  <label for="brand1"><span></span>Recordarme</label>
                  <a href="#" class="TransitionEffects">¿Olvidó su contraseña?</a>
                </li>
              </ul>
              <div class="wrapper">
                <input class="btnAccess" type="submit" id="button-login" value="INICIAR SESIÓN">
                <p class="MaTopForty letter-spacing-one">Registrar Nueva Cuenta <span>→</span> <a class="registeraa" href="#"> ¡Registro gratis!</a></p>
                <div class="clear"></div>
              </div>
        </form>
    </div>
  </div>
</div>

if (empty($username) === true || empty($password) === true) {
            $message = "Es necesario introducir un nombre de usuario y contraseña";
         } elseif ($username != $UsernamaDB) {
            $message = "El 'Usuario' que has introducido no coincide. ";
         } elseif ($save_passw != $passwordDB) {
            $message = "Tu 'Contraseña' introducido no coincide. ";
         } elseif($save_passw == $passwordDB && $username == $usernamaDB){
            $_SESSION["id_user"] = 1; // lo que quieras poner en la variable
            $con->query("DELETE FROM login_attempts WHERE ip = '$ip'");
         }

$message = "El 'Usuario' que has introducido no coincide. ";
echo 'username: '.$username.' / DB: '.$usernamaDB;