Wordpress Page not loading correct with Stylepath

I have got an error in my code and I cant find why and where it orginates. But I know the template isnt loading correct. I believe the problem could start in the code below. The problem started when I changed echo site_url to echo get_post_type_archive_link.

single-event.php

<?php 
    get_header();
while(have_posts()) {
    the_post(); ?>

<div class="page-banner">
      <div class="page-banner__bg-image" style="background-image: url(<?php echo get_theme_file_uri('/images/ocean.jpg') ?>)"></div>
      <div class="page-banner__content container container--narrow">
        <h1 class="page-banner__title"><?php the_title();?></h1>
        <div class="page-banner__intro">
          <p>DONT FORGETT TO REPLACE ME LATER!!</p>
        </div>
      </div>
    </div>

        

        <div class="container container--narrow page-section">

        <div class="metabox metabox--position-up metabox--with-home-link">
        <p>
          <a class="metabox__blog-home-link" href="<?php echo site_url('/blog'); ?>">
                        <i class="fa fa-home" aria-hidden="true"></i> Events Home</a> 
                        <span class="metabox__main"><?php the_title(); ?></span>
        </p>
      </div>

        
<div class="generic-content"><?php the_content();?></div>

    <h2>
<?php }
    get_footer();
?>

single.php

<?php 
    get_header();
while(have_posts()) {
    the_post(); ?>

<div class="page-banner">
      <div class="page-banner__bg-image" style="background-image: url(<?php echo get_theme_file_uri('/images/ocean.jpg') ?>)"></div>
      <div class="page-banner__content container container--narrow">
        <h1 class="page-banner__title"><?php the_title();?></h1>
        <div class="page-banner__intro">
          <p>DONT FORGETT TO REPLACE ME LATER!!</p>
        </div>
      </div>
    </div>

        

        <div class="container container--narrow page-section">

        <div class="metabox metabox--position-up metabox--with-home-link">
        <p>
          <a class="metabox__blog-home-link" href="<?php echo get_post_type_archive_link('event'); ?>">
                        <i class="fa fa-home" aria-hidden="true"></i> Blog Home</a> 
                        <span class="metabox__main">Posted by <?php the_author_posts_link(); ?> on <?php the_time('n.j.y'); ?> in <?php echo get_the_category_list(', '); ?></span>
        </p>
      </div>

        
<div class="generic-content"><?php the_content();?></div>

    <h2>
<?php }
    get_footer();
?>

Error message: