My rest-api setting is not working

I tried it with the TwentyTwenty-four theme and it works. I wrote to you because I am sure it is due to the theme.

I disabled plugins that are not related to the theme, the problem still persists. You can provide controls with the administrator account I specified in the hide content.

I don’t understand why these codes I added to the child theme give an error. Do you see any problems?

add_shortcode( ‘product_description’, ‘display_product_description’ );
function display_product_description( $atts ){
$atts = shortcode_atts( array(
‘id’ => get_the_id(),
), $atts, ‘product_description’ );

global $product;

if ( ! is_a( $product, ‘WC_Product’) )
$product = wc_get_product($atts[‘id’]);

$description = $product->get_description();

$first_sentence = strtok($description, ‘.’);

return $first_sentence . ‘.’;
}