Does Italy have a new policy?
The Aust Embassy in Rome website has some helpful info including a PDF of a doc written in English and Italian explaining that the Aust certificate is valid in Italy even if the QR code can't be read. They suggest carrying both the Aust certificate and the letter. See below link.
"The Australian Embassy in Rome has prepared a letter (in English and Italian) that may assist with confirming that Australia's vaccination certificates are recognised as equivalent to 'Super' Green Passes in Italy –
available here (PDF)."