Following up on our recent WhatsApp conversation:

We identified that the issue came from a plugin generating pages without setting the global $post variable.

This omission prevents the Language Switcher from retrieving the post ID.

For others encountering this problem, a workaround involves passing the post ID to the Language Switcher via a custom script, as demonstrated below:

add_action('lsw_get_current_post_id',function($post_id){
	
        // fetch the custom post id here
	return $post_id;
	
},999999,1);