Next and previous links don't work

what is the code of your custom query on that page template?

(if the code snippet is longer than 10 ines, please paste it into a https://pastebin.com/ and post the link to it here)

try to integrate the ‘paged’ parameter:
https://codex.www.ads-software.com/Function_Reference/WP_Query#Pagination_Parameters

My query is

<?php query_posts('cat=299'.get_the_title().'&post_status=publish,future');?>

	<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
	<h1><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h1>
	<p><?php the_content(); ?>
	<?php endwhile; else: endif; ?>

get_the_title() gets the title of the current post… placed here it was only breaking your query.

query_posts('cat=299&post_status=publish,future');

also, maybe try to integrate the ‘paged’ parameter:

<?php query_posts('cat=299&post_status=publish,future&paged=' . get_query_var('paged'));?>

Thanks! It works now.