Select problem add_action in function.php

I hope not to write silly things and be able to explain my problem. I wrote a plugin sketch where I access the database with some queries , you report the code that works :

<?php
/*
Plugin Name: Carica File
URI: Url del plugin
Description: Carica File schede prodotti
Author: Riccardo Version: 1.0
Author URI: http://lksnc.it/
License: GPL2
*/

// plugin path
$wp_plugin_dir = substr(plugin_dir_path(__FILE__), 0, -1);
define('RR_DIR', $wp_plugin_dir);

// plugin url
$wp_plugin_url = substr(plugin_dir_url(__FILE__), 0, -1);
define('RR_URL', $wp_plugin_url);

function rr_theme_options_panel(){
  add_menu_page('Theme page title', 'Carica File', 'manage_options', 'theme-options', 'rr_wps_theme_func', 'dashicons-media-document');
}
add_action('admin_menu', 'rr_theme_options_panel');

function rr_wps_theme_func(){
                echo '<div class="wrap"><div id="icon-options-general" class="icon32"><br></div><h2>Theme</h2></div>';

global $wpdb;
$RR_ID='5888';
echo $RR_ID.'<br>';

			//LEGGO TABELLA PER RECUPERARE SKU >>>> SELECT  <code>meta_value</code> FROM  <code>wp_postmeta</code> WHERE  <code>post_id</code> =  '5888' AND  <code>meta_key</code> =  '_sku'
			//META KEY (SKU) POTREBBE ESSERE ANCHE VUOTO NEL CASO MI FERMO E AVVISO DDK VIA MAIL
			$RR_SKU=$wpdb->get_row("SELECT * FROM $wpdb->postmeta WHERE post_id=". (int) $RR_ID ." AND meta_key='_sku'", ARRAY_A);
			$RR_SKU=$RR_SKU['meta_value'];
			echo $RR_SKU.'<br>';

			//LEGGO TABELLA PER RECUPERARE LINGUA >>>> SELECT <code>language_code</code>  FROM  <code>wp_icl_translations</code> WHERE  <code>element_id</code> =  '5888'
			$RR_lang=$wpdb->get_row("SELECT * FROM wp_icl_translations WHERE element_id=". (int) $RR_ID ."", ARRAY_A);
			$RR_lang=$RR_lang['language_code'];
			echo $RR_lang.'<br>';

			//COSTRUISCO STRINGA PER MODIFICARE POST_CONTENT IN TABELLA WP_POSTS
			$RR_product_description='example NEW TEXT PRODUCT ON CREATION';

			//ESEGUO QUERY UPDATE >>>>>> UPDATE  <code>wp_posts</code> SET  <code>post_content</code> =  'descrizione xxx prodotto' WHERE  <code>ID</code> =  '5888'
			$wpdb->update(
					'wp_posts',
					array(
						'post_content' => $RR_product_description,	// stringa
					),
					array( 'ID' => $RR_ID ),
					array(
						'%s',	// valore1
					),
					array( '%d' )
			);

			//creo cartelle per contenere schede >>>>>> archividdk/prodotti/sku/lang/msds & archividdk/prodotti/sku/lang/data

$xmess='ID: '.$RR_ID.' Sku: '.$RR_SKU.' Lang: '.$RR_lang;
mail('[email protected]','new job published',$xmess);
echo $xmess;

}
?>

select to access the database and retrieve the data , the update changes the content as intended .

The same query ( SELECT ) put in function.php rather not produce any RESULT , WHILE update keeps working .

add_action( 'transition_post_status', function ( $new_status, $old_status, $post )
{

    if( 'publish' == $new_status && 'publish' != $old_status && $post->post_type == 'product' ) {
		//RECUPERO ID PRODOTTO
        $RR_ID=$post->ID;
		global $wpdb;

					//LEGGO TABELLA PER RECUPERARE SKU >>>> SELECT  <code>meta_value</code> FROM  <code>wp_postmeta</code> WHERE  <code>post_id</code> =  '5888' AND  <code>meta_key</code> =  '_sku'
					//META KEY (SKU) POTREBBE ESSERE ANCHE VUOTO NEL CASO MI FERMO E AVVISO DDK VIA MAIL
					$RR_SKU=$wpdb->get_row("SELECT * FROM $wpdb->postmeta WHERE post_id=". (int) $RR_ID ." AND meta_key='_sku'", ARRAY_A);
					$RR_SKU=$RR_SKU['meta_value'];

					//LEGGO TABELLA PER RECUPERARE LINGUA >>>> SELECT <code>language_code</code>  FROM  <code>wp_icl_translations</code> WHERE  <code>element_id</code> =  '5888'
					$RR_lang=$wpdb->get_row("SELECT * FROM wp_icl_translations WHERE element_id=". (int) $RR_ID ."", ARRAY_A);
					$RR_lang=$RR_lang['language_code'];

					//COSTRUISCO STRINGA PER MODIFICARE POST_CONTENT IN TABELLA WP_POSTS
					$RR_product_description='example NEW TEXT PRODUCT ON CREATION';

					//ESEGUO QUERY UPDATE >>>>>> UPDATE  <code>wp_posts</code> SET  <code>post_content</code> =  'descrizione xxx prodotto' WHERE  <code>ID</code> =  '5888'
					$wpdb->update(
							'wp_posts',
							array(
								'post_content' => $RR_product_description,	// stringa
							),
							array( 'ID' => $RR_ID ),
							array(
								'%s',	// valore1
							),
							array( '%d' )
					);

					//creo cartelle per contenere schede >>>>>> archividdk/prodotti/sku/lang/msds & archividdk/prodotti/sku/lang/data

		$xmess='ID: '.$RR_ID.' Sku: '.$RR_SKU.' Lang: '.$RR_lang;
		mail('[email protected]','new job published',$xmess);

    }
}, 10, 3 );

Can someone explain to me where I’m wrong ? I’d be very grateful . Riccardo