Second Loop Showing Only One Post on Single Post Page

The answer to the above question was very simple and answered by a kind person at the WordPress Support forum. There was an extra div that was causing problems. Remove the last div, and it all worked out fine. A very simple solution, but one I wouldn’t have known that could cause that much trouble. I hope anyone else looking for a similar solution checks on the divs, because it is very important that the endif statements do not get separated off from their intended function. In this case, the extra div was responsible.

The new code looks like this:

<div id="blogcontainer" onmouseover="RollOff1()" onmouseout="RollOff2()">
<?php query_posts('post_type=post') ?>
    <?php if (have_posts()): while (have_posts()) : the_post(); ?>
<div class="postcontainer" id="post-<?php the_ID(); ?>">
<div class="thumb">
            <?php if ( has_post_thumbnail()) : // Check if thumbnail exists ?>
        <a href="https://wordpress.stackexchange.com/questions/320515/<?php the_permalink(); ?>" title="<?php the_title(); ?>">
            <?php the_post_thumbnail(array(100,100)); // Declare pixel size you need 
            inside the array ?>
        </a>
    <?php endif; ?>


    </div>
   <div class="topblock"><div class="titleblock">   <a href="https://wordpress.stackexchange.com/questions/320515/<?php the_permalink(); ?>" title="<?php the_title(); ?>"><?php the_title(); ?></a></div>
 <div class="moreblock"><a href="https://wordpress.stackexchange.com/questions/320515/<?php the_permalink(); ?>">MORE ></a></div>
  </div>
  <div class="block">
  <div class="date"><p><span class="date"><?php the_time('F j, Y'); ?></span></p> 
  </div>
<?php html5wp_excerpt('html5wp_index'); ?>
  </div>
                                   </div>
    <?php endwhile; ?>

    <?php else: ?>

            <h2><?php _e( 'Sorry, nothing to display.', 'html5blank' ); ?></h2>

    <?php endif; ?>
    </div>

   </div>



  <?php get_footer(); ?>