Porque me da este error Not Found

[Fernarey1810]

Not Found
The requested URL /product.php was not found on this server.

Archivo product.php

Código PHP:

<?php
 
require_once 'include/url_redirect.inc.php';
 
fix_category_product_url();
 
echo 'You have selected product #' . $_GET['product_id'] .
     ' from category #' . $_GET['category_id'];
 
?>
 

Archivo url_redirect.inc.php

Código PHP:

<?php
 
define('SITE_DOMAIN', 'localhost/Apache/Capitulo4');
 
$GLOBALS['products'] = array
      ("45" => "Belt Sander",
       "31" => "Link Juice",
       "42" => "AJAX PHP Book");
$GLOBALS['categories'] = array
      ("12" => "Carpenter's Tools",
        "6" => "SEO Toolbox",
        "2" => "Friend's Shed");
 
function fix_category_product_url()
{   
  
  $proper_url = get_proper_category_product_url();
 
  if (SITE_DOMAIN . $_SERVER['REQUEST_URI'] != $proper_url) 
  { 
    header('HTTP/1.1 301 Moved Permanently');
    header('Location: ' . $proper_url);
    exit();     
  }
}
 
 
function get_proper_category_product_url()
{
  
  $product_id = $_GET['product_id'];
  $category_id = $_GET['category_id'];
  
  $product_name = $GLOBALS['products'][$product_id];
  $category_name = $GLOBALS['categories'][$category_id];
  
  $proper_url = make_category_product_url($category_name, $category_id, 
                                          $product_name, $product_id);
  
  return $proper_url;
}
 
?>
 

Archivo .htaccess

RewriteEngine On

# Rewrite numeric URLs
RewriteRule ^Products/C([0-9]*)/P([0-9]*)\.html$ /product.php?category_id=$1&product_id=$2 [L]

# Rewrite keyword-rich URLs
RewriteRule ^Products/.*-C([0-9]+)/.*-P([0-9]+)\.html$ /product.php?category_id=$1&product_id=$2 [L]