Nav Links Disappeared

I have a webcomic that used to have a nav menu above and below the comic (you guys helped a lot with getting it working). Suddenly, sometime in the last 24 hours or so, the second menu (the one below the webcomic) disappeared. I'm not quite sure what happened, especially since I haven't been fiddling with any of the php or css files recently. Hoping you guys can take a quick look and point me in the right direction. Note, I have this code in my function.php (and haven't edited it in a couple weeks).

edit: One thought I just had is that I recently set up the site to force https. I don't see why that would impact the second nav bar, but I wanted to mention it since that's the only significant thing I've done recently.

<?php

add_action( 'generate_before_main_content', function() {
    if ( function_exists( 'previous_post_link' ) && function_exists( 'next_post_link' ) ) {
		echo '<div class="post-navigation">';
		echo  previous_post_link(); //Older Link using max_num_pages
		echo  next_post_link(); //Newer Link using max_num_pages
		echo '</div>'; 
    }
} );

add_action( 'generate_paging_navigation', function() {
    if ( function_exists( 'previous_post_link' ) && function_exists( 'next_post_link' ) ) {
		echo '<div class="post-navigation">';
		echo  previous_post_link(); //Older Link using max_num_pages
		echo  next_post_link(); //Newer Link using max_num_pages
		echo '</div>'; 
    }
} );

add_filter( 'next_post_link', function( $output, $format, $link, $post ) {
	
	$currentID = get_the_ID();
  	$args = array(
	  	'numberposts' => 1,
	  	'order'    => 'ASC',
	  	'orderby' => 'rand',
	  	'post__not_in' => array( $currentID ),
	);
  
    $random_post = get_posts( $args );
	
    if ( ! $post ) {
       	  $next = sprintf(
        '<a class="next-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $post ),
        $post->post_title
	);

	  $random_post = sprintf(
        '<a class="random-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $random_post[0]->ID ),
        get_the_title( $random_post[0]->ID )
    );
	
	$last_post = get_posts( 'numberposts=1&order=ASC' );

    $last_post = sprintf(
        '<a class="last-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $last_post[0]->ID ),
        get_the_title( $last_post[0]->ID )
    );
	      return $random_post . $next . $last_post;
    }
	
	else {
		  $next = sprintf(
        '<a class="next-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $post ),
        $post->post_title
    );
  
    $random_post = sprintf(
        '<a class="random-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $random_post[0]->ID ),
        get_the_title( $random_post[0]->ID )
    );
    
	$last_post = get_posts( 'numberposts=1&order=ASC' );

    $last_post = sprintf(
        '<a class="last-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $last_post[0]->ID ),
        get_the_title( $last_post[0]->ID )
    );
	   return $random_post . $next . $last_post;
	}
	
}, 10, 4 );

add_filter( 'previous_post_link', function( $output, $format, $link, $post ) {
    if ( ! $post ) {
        $prev = sprintf(
        '<a class="previous-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $post ),
        $post->post_title
    );

 $latest_post = get_posts( 'numberposts=1' );

    $latest_post = sprintf(
        '<a class="latest-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $latest_post[0]->ID ),
        get_the_title( $latest_post[0]->ID )
    );
	
	    return $latest_post . $prev;
    }
  else{
    $prev = sprintf(
        '<a class="previous-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $post ),
        $post->post_title
    );

 $latest_post = get_posts( 'numberposts=1' );

    $latest_post = sprintf(
        '<a class="latest-post" href="%1$s" title="%2$s"></a>',
        get_permalink( $latest_post[0]->ID ),
        get_the_title( $latest_post[0]->ID )
    );
	
    return $latest_post . $prev;
  }
}, 10, 4 );