19
Well, I haven't looked extensively, but it looks as if cod_lista, the item_name you're using, is not actually in the URL? The item name needs to be in the URL (unless you're going to do some extensive hacking of how the notification system works), because the notification system checks for the value of that item in the URL and determines whether or not to send a notification based on what it finds there.
In the code you made available, in the file liberar.php, the $cod_lista variable is actually derived from a database query, not from the URL.
So without digging further, my hunch right now would be that you have do not have the right variables in the URL in order for the notification trigger to actually operate correctly.
I made some extensive notes in the comments for the notification class, in the old wiki, before it was taken down, about how to do notifications without a URL parameter in place. I believe ackbarr still has a copy of the comments from that wiki on a hard drive somewhere.
Good luck,
--Julian