This issue was rectified by Amazon, apparently the country settings for my account were associated with amazon.com and not .com.au? This was rectified promptly after I left this review. I've left my experience here regardless: "I was hoping this device would be easy to use for family members etc. However it is extremely difficult to get past the initial sign in during the 2FA sign in process where the device prompts you to go to amazon.com.au/code, which isn't even a valid URL! I eventually managed to guess to go to amazon.com/code (for anyone else having the same trouble). Not really good enough!"
Now that I've spent some time with the device (after logging in), I'm deeply impressed with the playback ability of the device, it was able to play every codec it has advertised as well as PGS and SRT subtitles without any issues. It really is fantastic for the cost of the product, able to compete with my Nvidia Shield. You pay in turn with the advertising embedded into the software and the remote, which takes up a substantial amount of the UI.