How to censor words with Amazon Polly?

Hi, I'm trying to put a lexicon in Amazon Polly console in order to censor some stopwords. My .xml file is accepted, but there is no result with the spoken input.

This is my script

<?xml version="1.0" encoding="UTF-8"?>

<lexicon version="1.0" xmlns="http://www.w3.org/2005/01/pronunciation-lexicon" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.w3.org/2005/01/pronunciation-lexicon http://www.w3.org/TR/2007/CR-pronunciation-lexicon-20071212/pls.xsd" alphabet="ipa" xml:lang="it-IT"> <lexeme> <grapheme>parola uno</grapheme> <alias></alias> </lexeme> <lexeme> <grapheme>parola due</grapheme> <alias></alias> </lexeme> <lexeme> <grapheme>parola tre</grapheme> <alias></alias> </lexeme> <lexeme> <grapheme>parola quattro</grapheme> <alias></alias> </lexeme> </lexicon>

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I can't understand the error, Thank you very much if you can help me!