Why does this post appear as “Page Not Found”?

Heya – I’m working on this site: https://jen-novak-consulting.theportlandco.com/weekly-web-guide-to-the-local-scene

And when you visit that link, which is to a single unique “Post” (not a “Page”) it is telling me that it’s “Page Not Found”. But if you select the first category (which is listed in the middle column) it shows the posting just fine…

I have a single.php file:

<?php
get_header();

/*
Template Name: Internal
*/
?>

	<!-- BEGINNING OF ROW-1 -->
	<!-- BEGINNING OF ROW-1 -->
	<div class="row-1">
		<?php wp_list_pages('title_li='); ?>
	</div>

	<!-- BEGINNING OF ROW-2 -->
	<!-- BEGINNING OF ROW-2 -->
	<div class="row-2">

		<!-- BEGINNING OF ROW-2-COL-1 -->
		<div class="row-2-col-1" id="row-2-col-1-alternate">
			<img src="/wp-content/themes/jen-novak-consulting/images/logo.png" class="logo" />

			<div class="archives"><?php wp_get_archives('title_li=&type=postbypost&limit=1'); ?> <span style="float: right;"><?php wp_get_archives('limit=3'); ?></span></div>

			<div class="categories">
				<?php wp_list_categories('&title_li='); ?>
			</div>

			<p class="copyright">Copyright 2009 Jen Novak All Rights Reserved</p>
		</div><!-- END OF ROW-2-COL-1 -->

		<!-- BEGINNING OF ROW-2-COL-3 -->
		<div class="row-2-col-3" id="row-2-col-1-alternate">
	<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

		<div class="navigation">
			<div class="alignleft"><?php previous_post_link('&laquo; %link') ?></div>
			<div class="alignright"><?php next_post_link('%link &raquo;') ?></div>
		</div>

		<div <?php post_class() ?> id="post-<?php the_ID(); ?>">
			<h2><?php the_title(); ?></h2>

			<div class="entry">
				<?php the_content('<p class="serif">Read the rest of this entry &raquo;</p>'); ?>

				<?php wp_link_pages(array('before' => '<p><strong>Pages:</strong> ', 'after' => '</p>', 'next_or_number' => 'number')); ?>
				<?php the_tags( '<p>Tags: ', ', ', '</p>'); ?>

				<p class="postmetadata alt">
					<small>
						This entry was posted
						<?php /* This is commented, because it requires a little adjusting sometimes.
							You'll need to download this plugin, and follow the instructions:
							https://binarybonsai.com/archives/2004/08/17/time-since-plugin/ */
							/* $entry_datetime = abs(strtotime($post->post_date) - (60*120)); echo time_since($entry_datetime); echo ' ago'; */ ?>
						on <?php the_time('l, F jS, Y') ?> at <?php the_time() ?>
						and is filed under <?php the_category(', ') ?>.
						You can follow any responses to this entry through the <?php post_comments_feed_link('RSS 2.0'); ?> feed.

						<?php if (('open' == $post-> comment_status) && ('open' == $post->ping_status)) {
							// Both Comments and Pings are open ?>
							You can <a href="#respond">leave a response</a>, or <a href="<?php trackback_url(); ?>" rel="trackback">trackback</a> from your own site.

						<?php } elseif (!('open' == $post-> comment_status) && ('open' == $post->ping_status)) {
							// Only Pings are Open ?>
							Responses are currently closed, but you can <a href="<?php trackback_url(); ?> " rel="trackback">trackback</a> from your own site.

						<?php } elseif (('open' == $post-> comment_status) && !('open' == $post->ping_status)) {
							// Comments are open, Pings are not ?>
							You can skip to the end and leave a response. Pinging is currently not allowed.

						<?php } elseif (!('open' == $post-> comment_status) && !('open' == $post->ping_status)) {
							// Neither Comments, nor Pings are open ?>
							Both comments and pings are currently closed.

						<?php } edit_post_link('Edit this entry','','.'); ?>

					</small>
				</p>

			</div>
		</div>

	<?php comments_template(); ?>

	<?php endwhile; else: ?>

		<p>Sorry, no posts matched your criteria.</p>

<?php endif; ?>
		</div><!-- END OF ROW-2-COL-3 -->
	</div><!-- BEGINNING OF ROW-2 -->
<?php get_footer(); ?>