I can’t log-in to the Veloce website (https://www.velocelounges.com), as I don’t have one of these cards right now. However, if a lounge is listed, you should be able to access it just with your credit card (But I’ve never tried). I have heard that some lounges have been blanking-out
Priority Pass is a separate, competing programme to Veloce (included as part of the American Express Platinum card package, FWIW). You don’t get a Priority Pass card with the ANZ Black cards, so I believe the receptionist was in error, or that “Something’s gone wrong” with Veloce’s relationship with that lounge. I’d try whining to Veloce and the ANZ Black concierge and see if this gets you some oil.