I made other tests.
-No, it does not work for other products.
-yes, the plugin "HikaShop Product Wait List Notification plugin" is eabled.
-yes, hikashop is able to send email to user; the emails are properly sent.
-yes i receive the email from joomla system.
So, i tried with my test site where the email system is not configure preperly. when i trigger the hika-cron i have:
some SMTP errors due to bad configuration
but i have the right work of hika-cron-plugins.
You can see that from my screenshots: the first one from official site and the second one from test site.