The {{custom_field}}
template tag is set to return single values. If the custom field you’re using is returning an array, it won’t work.
You could try this to debug:
add_shortcode( 'embed_file', function() {
ob_start();
$current_post = get_queried_object();
$embed_file = get_field( 'report_file', $current_post );
var_dump($embed_file);
$report_file_url = $embed_file['url'];
echo $report_file_url;
return ob_get_clean();
} );