I am not familiar with the theme you are using but it looks like it is not rendering the Ad details page at all, it only shows the description user entered in the [adverts_add].
This might be because the template is either not using the_content filter or the_content is not displayed inside the loop.
The best way to fix it would be to create a single-advert.php template file as explained here https://wpadverts.com/documentation/child-themes-and-templates/ in “Custom Post Type Template” section and then replace <?php the_content() ?> (or other part of the code responsible for displaying the content) with
$post_id = get_the_ID();
$post_content = get_post( $post_id )->post_content;
$post_content = wp_kses($post_content, wp_kses_allowed_html( 'post' ) );
$post_content = apply_filters( "adverts_the_content", $post_content );
include apply_filters( "adverts_template_load", ADVERTS_PATH . 'templates/single.php' );
Also if it worked previously but not now and you have installed some plugin recently it is possible that there is a conflict between your plugin and WPAdverts in this case you can try disabling the recently installed plugin and see if it helps.
While debugging you might also want to disable the WP Fastest Cache plugin so the changes on site will be visible on site live.
