If it is over 6 months it will have been deactivated as with all telcos. It is also quite likely you will have lost your mobile number.
Optus support or an optus shoo is you next step or order a new Sim online with a new mobile number.
Hey @JeremyG - if this is related to a prepaid service, your number may have been deactivated if you haven't recharged in a while. If you'd like us to double check if your number is still active, please send me a private message here with the following info:
Date of birth:
Are you the primary account holder: Y/N
Just so you're aware, if the number has been deactivated we may not be able to retrieve it for you, but we'll see if there's anything we can do to help.