Weird 404 page – not from theme

So the problem is wordpress is not using 404.php theme page

You need to provide more details about the issue.
It looks like your 404.php template is not been working, there could be possibility that you have not coded it properly.

Please read the Forum Guidelines and supply enough information for one to analyze the issue.

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I’m using accesspress store theme. Here’s code it’s 404.php file

<?php
/**
 * The template for displaying 404 pages (not found).
 *
 * @package AccessPress Store
 */

get_header(); ?>

<main id="main" class="site-main" role="main">
	<div id="primary" class="content-area">
		<section class="error-404 not-found">
			<header class="page-header">
				<h1 class="page-title"><?php _e( 'Oops! That page can&rsquo;t be found.', 'accesspress-store' ); ?></h1>
			</header><!-- .page-header -->

			<div class="page-content">
				<p><?php _e( 'It looks like nothing was found at this location. Maybe try one of the links below or a search?', 'accesspress-store' ); ?></p>
			</div><!-- .page-content -->

			<div class="number404">
				404 
				<span>error</span>   
			</div>
		</section><!-- .error-404 -->		
	</div><!-- #primary -->
</main><!-- #main -->
<?php get_footer();

It is theme 404.php file, I haven’t edited it. I wanted to use 404custom error page plugin but it didn’t work. It showed error I was writing in 1st post

Guuuys, help please.

Also, if you can check the Apache module called mod_rewrite is on for the server?
Can you tell me what permalink settings you are using for your site? If you are using anything apart from plain try switching to plain permalink settings and check if your 404 template works or not.