Custom Post type category pages template and loop

You may alter the main query before the loop, but it’s crucial to reset the main query afterwards. Otherwise you’ll probably run into problems elsewhere.

Disclaimer: Doing this is officially discouraged by WordPress here. However, in my experience it works perfectly to achieve the behaviour you want. Just don’t forget to add wp_reset_query(); after closing the loop.

<?php query_posts('post_type=event'); ?>
  <?php if ( have_posts() ): while ( have_posts() ): the_post(); ?>

    <!-- Stuff happening inside the loop -->

  <?php endwhile; endif; ?>
<?php wp_reset_query(); ?>

Another approach (slightly more complicated but without altering the main query) would be:

<?php $args = array( 'posts_per_page' => 10, 'post_type' => 'event', 'post_status' => 'publish' ); ?>
<?php $get_category_posts = get_posts( $args ); ?>
<?php foreach ( $get_category_posts as $post ) : setup_postdata( $post ); ?>

  <!-- Stuff happening inside our custom 'loop' -->

<?php endforeach; ?>
<?php wp_reset_postdata(); ?>

According to the 2nd solution, your PHP-File should look like this:

<?php get_header(); ?>

<?php $args = array( 'posts_per_page' => 10, 'post_type' => 'event', 'post_status' => 'publish' ); ?>
<?php $get_category_posts = get_posts( $args ); ?>
<?php foreach ( $get_category_posts as $post ) : setup_postdata( $post ); ?>

  <div class="class1">
    <div class="class2">
      <div class="class3">

        <?php print_r( get_post_meta( get_the_ID() ) ); // Just for demo purposes ?>

        <?php // $url = esc_url( get_post_meta( get_the_ID(), 'video_oembed', true ) ); ?>
        <?php // $embed = wp_oembed_get( $url ); ?>

        <div class="class4">
          <iframe id="class_frame" width="560" height="315" src="https://www.youtube.com/watch" allowfullscreen frameborder="0"></iframe>
        </div>
      </div>
      <div class="class6">
        <h1><?php the_title(); ?></h1>
        <p><?php the_content(); ?></p>
      </div>
    </div>
  </div>

<?php endforeach; ?>
<?php wp_reset_postdata(); ?>

<?php get_footer(); ?>

If this doesn’t work it might be that you’re working in the wrong template file. Without knowing your project my guess would be that it should be archive-event.php

Update:

It turned out to be taxonomy-event.php in this case.