Since Porto is a paid theme, I can’t download and test it with our plugin.
But these are the things you could try:
Try switching to default themes that come with WordPress like Twenty Twenty-Three and see if it’s working on a single product page. If it is, one possibility is Porto theme probably changes something with how Woocommerce hook woocommerce_single_product_summary works. Sometimes themes do that.
Some themes try to rearrange the presentation on Woocommerce single product pages, so they might remove and add things to this hook, which causes our plugin to not work as intended.
Try adding the following code to your functions.php and see if it works:
add_action( 'woocommerce_single_product_summary', 'thp_ysxfw_you_save_single_product_page', 9999 );
Another thing to try is to deactivate your plugins one by one and see if it works when these plugins are not active. This is to eliminate the possibility that a plugin might cause the issue.
