Hi,
I called the department a few days ago regarding this and was told that the invite will be sent via email and should also appear in your immi inbox. Just to be sure, keep checking your immi account.
Upon checking the Stonnington Council ceremony dates there are a few more for the rest of this year.
Ceremonies are scheduled for:
Tuesday 20 September 2022
Wednesday 12 October 2022
Wednesday 16 November 2022
Tuesday 6 December 2022
Wednesday 7 December 2022
Also, based on the advice from the DHA. You receive your ceremony invite between 3-6 months after your approval. So hopefully it should be within the next 2 months.