Next and Previous post buttons have disappeared

Is there any pagination enable, disable options on theme? Make sure about it first. If no let me know.
Thanks

No, I believe there is no pagination enable/disable option.

I also just noticed that if I am writing a post and click the preview button before it is published, sometimes the buttons are there and other times, the buttons are not there. Looks like it is randomly happening.

By our inspection we found that the div for pre/next is there. However, it is not displaying. Can you please paste your single.php & content-single.php file codes?

Sorry, another update to this problem. I noticed that when I click the previous and next posts button, there is a space that appears in the bottom of the single post page where the buttons go but there is nothing there other than the really faint line separating the previous and next posts areas.

There is my single.php
<?php global $optimizer;?>
<?php get_header(); ?>

<div class=”post_wrap layer_wrapper”>

<div id=”content”>
<div class=”center”>
<!–POST START–>
<div class=”single_wrap<?php if ( !is_active_sidebar( ‘sidebar’ ) ) { ?> no_sidebar<?php } ?>”>
<div class=”single_post”>

<?php if(have_posts()): ?><?php while(have_posts()): ?><?php the_post(); ?>
<div <?php post_class(); ?> id=”post-<?php the_ID(); ?>”>

<!–EDIT BUTTON START–>
<?php if ( is_user_logged_in() && is_admin() ) { ?>
<div class=”edit_wrap”>
“>
<?php _e(‘Edit’,’optimizer’); ?>

</div>
<?php } ?>
<!–EDIT BUTTON END–>

<!–POST START–>
<div class=”single_post_content”>

<h1 class=”postitle entry-title”><?php the_title(); ?></h1>
<!–POST INFO START–>
<?php if (!empty ($optimizer[‘post_info_id’]) || is_customize_preview()) { ?>
<div class=”single_metainfo <?php if (empty($optimizer[‘post_info_id’])){ echo ‘hide_singlemeta’;}?>”>
<!–DATE–>
<i class=”fa-calendar”></i><?php the_time( get_option(‘date_format’) ); ?>
<!–AUTHOR–>
<i class=”fa-user”></i><?php global $authordata; $post_author = “ID, $authordata->user_nicename ).”\”><span class=’fn’>”.get_the_author().”</span>\r\n”; echo $post_author; ?>
<!–COMMENTS COUNT–>
<i class=”fa-comments-o”></i><?php if (!empty($post->post_password)) { ?>
<?php } else { ?><div class=”meta_comm”><?php comments_popup_link( __(‘0 Comment’, ‘optimizer’), __(‘1 Comment’, ‘optimizer’), __(‘% Comments’, ‘optimizer’), ”, __(‘Off’ , ‘optimizer’)); ?></div><?php } ?>
<!–CATEGORY LIST–>
<i class=”fa-th-list”></i><div class=”catag_list”><?php the_category(‘, ‘); ?></div>
</div>
<?php } ?>
<!–POST INFO END–>

<!–POST CONTENT START–>
<div class=”thn_post_wrap”>

<?php the_content(); ?>

</div>
<div style=”clear:both”></div>
<div class=”thn_post_wrap wp_link_pages”>
<?php wp_link_pages(‘<p class=”pages”>‘.__(‘Pages:’, ‘optimizer’).’ ‘, ‘</p>’, ‘number’); ?>
</div>
<!–POST CONTENT END–>

<!–POST FOOTER START–>
<div class=”post_foot”>
<div class=”post_meta”>
<?php if( has_tag() ) { ?>
<div class=”post_tag”>
<div class=”tag_list”>
<?php if(get_the_tag_list()) {
echo get_the_tag_list(‘

• <i class=”fa-tag”></i>’,’
• <i class=”fa-tag”></i>’,’

‘);
}
?>
</div>
</div>
<?php } ?>
</div>
</div>
<!–POST FOOTER END–>

</div>
<!–POST END–>
</div>

<?php endwhile ?>

<?php endif ?>

<?php if (!empty ($optimizer[‘post_nextprev_id’]) || is_customize_preview()) { ?>
<!–NEXT AND PREVIOUS POSTS START–>
<?php if ( get_post_status ( get_the_ID() ) !== ‘private’ ) { ?>
<?php get_template_part(‘framework/core’,’nextprev’); ?>
<?php } ?>
<!–NEXT AND PREVIOUS POSTS END–>
<?php }?>

<!–COMMENT START: Calling the Comment Section. If you want to hide comments from your posts, remove the line below–>
<?php if (!empty ($optimizer[‘post_comments_id’]) || is_customize_preview()) { ?>
<div class=”comments_template <?php if (empty($optimizer[‘post_comments_id’])){ echo ‘hide_comments’; }?>”>
<?php comments_template(”,true); ?>
</div>
<?php }?>
<!–COMMENT END–>

</div>
</div>

<!–SIDEBAR START–>
<?php get_sidebar(); ?>
<!–SIDEBAR END–>

</div><!–center class END–>
</div><!–#content END–>
</div><!–layer_wrapper class END–>

<?php get_footer(); ?>

I can’t find the content-single.php file.