An interesting situation: back in 2017 I went overseas with the intention of staying there (I'm a UK dual-citizen) and when I did, I unenrolled from the Australian Electoral Commission using their "unenroll me, I'm permanently leaving" form.
Later that year I came back deciding that I didn't want to do that, but I never re-enrolled and subsequently haven't voted in any election since without any sort of consequence and honestly, for me I kind of like this situation. I can't find any information anywhere about a penalty for doing this, only information about if you've never enrolled before. The penalty for not voting is for just that, enrolled citizens not voting. Not for being unenrolled.