Crusader Kings 3 released everywhere in the world this week except for Australia, although you can still play it on Xbox Game Pass.
It appears that the game was refused classification in Australia after the game was submitted to the IARC (where digital games are submitted for review). Nothing about the game suggests that it should have been refused classification, meaning that it could just be an administrative error with the submission process.
As Kotaku reports, the game is still available to play on Xbox Game Pass and it has an MA15+ rating, so it would be unlikely that the classification refusal hasn’t been rectified. You can’t buy the game on Stream though, with the below message appearing: “In agreement with the publisher, Crusader Kings III is currently not available for purchase in your region”.