Author.php page does not show information

Here’s the full code. The page is normally called up using https://www.monamouchtim.com/author/lucas/ (or another username, which translates to https://www.monamouchtim.com/?author_name=lucas .

<?php get_header(); ?>
<div id="content" class="narrowcolumn">
<!-- This sets the $curauth variable -->
<?php
if(get_query_var('author_name')) :
$curauth = get_userdatabylogin(get_query_var('author_name'));
else :
$curauth = get_userdata(get_query_var('author'));
endif;
?>

<h2><?php echo $curauth->user_nickname; ?>'s Profile:</h2>
<?php echo $curauth->user_description; ?>

<h2>Posts by <?php echo $curauth->user_nickname; ?>:</h2>

<ul>
<!-- The Loop -->
<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
<li>
<a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link: <?php the_title(); ?>">
<?php the_title(); ?></a>,
<?php the_time('d M Y'); ?> in <?php the_category('&');?>
</li>

<?php endwhile; else: ?>
<p><?php _e('No posts by this author.'); ?></p>

<?php endif; ?>
<!-- End Loop -->
</ul>
</div>
<?php get_sidebar(); ?>
<?php get_footer(); ?>

Note:
https://www.monamouchtim.com/author/tiff/

Actually works… but not the others… ??

For what it is worth, I am having the same problems with the author.php page not showing information for some of the authors while showing it for others. Seems rather random too.

These work:

https://deviouslyartistic.com/author/hakfest/
https://deviouslyartistic.com/author/krash/

These do *not* work:

https://deviouslyartistic.com/author/gracie/
https://deviouslyartistic.com/author/jark/ (this is the admin account)

If anyone has any ideas then it would be greatly appreciated. ??