Hey there Georgiac0806,
Do you mean a PUK code?
If not, please leave Optus a message for further assistance and someone will get back to you as soon as possible.
You're using the SIM with an an unlocked handset? Sounds odd.
SIM cards do have an expiry date, but given it's a brand new SIM - I doubt that it's the case.
If you do not have a working service with any provider, I’d really suggest messaging us on Social Media, either Facebook or Twitter. They do have a point of escalation for the following urgent enquiries:
Ah, great! Thanks for the update.
Appreciated. Stay safe.