You don't see that every day but multiple citizenship aren't unusual. Your VPN usage complicates things and makes it difficult for the casino to know where you were at the moment of playing. If the IP logs don't show you played from New Zealand, the casino won't be able to know it. If you were aware that Australia was a banned territory, why access the casino through an Australian VPN server? It's also possible that you only found out about the restriction after the casino told you. The next thing that doesn't go in your favor is you entering an Australian address and submitting an Australian PoA.   

I am curious what decision CasinoGuru will make and in whose favor the verdict will be.