404 error on https://site.com/page/2/

Hi,
I have troubles with pagination. I found lot of threads and fixs about that, but nothing helped me. I also tried to set number of posts per page to less number than 10 (1, 5, 9 – nothing doesnt work).

I found that this bug have lot of users with older WP version, but I′m running version 4.0.1. Also, I have this problem on index (main) page, where are all posts sorted by the newest.

Here is my includes/pagination.php:

?<div class="paginate">
	<?php
	if(function_exists('wp_pagenavi'))
		wp_pagenavi();
	else { ?>
		<div class="pagination">
			<ul>
				<li class="left"><?php next_posts_link(esc_attr__('BACK', 'Couponize')); ?></li>
				<li class="right"><?php previous_posts_link(esc_attr__('NEXT', 'Couponize')); ?></li>
			</ul>
		</div>
	<?php } ?>
</div>
<div class="clear"></div>

Do you see any problem here? Or may I paste any other source code?

Thanks,
Jack