opencart 2.3. Error when redirecting to the /sitemap page. how to solve?

Question

opencart

Prompt plz. when going to the /sitemap.xml page, a file with such content is downloaded, instead of being transferred to the /index.php?route=extension/feed/google_sitemap page

<?php

opcache_reset();

ini_set('display_errors', 1);
ini_set('display_startup_errors', 1);
error_reporting(E_ALL);

// Version
define('VERSION', '2.3.0.2.5');

// Configuration
if (is_file('config.php')) {
  require_once('config.php');
}

// Install
if (!defined('DIR_APPLICATION')) {
  header('Location: install/index.php');
  exit;
}

// Startup
require_once(DIR_SYSTEM . 'startup.php');

start('catalog');

This is the first time I've come across such a moment. This is mistake ?
At the same time, the page /index.php?route=extension/feed/google_sitemap works and there is a site there .. But when you add the page /index.php?route=extension/feed/google_sitemap to search.google, it does not read it.