We'll normally come across this issue if there's a slight error in the email address you've registered. For example, an incorrect digit.
Send the Optus Sport Social service team a message - this is the forte' . They'll go in and double check the email address that's been registered as your Optus Sport username. If there's an error, they'll go in and amend it for you and send out a new password reset email.
Let us know how it all goes 🙂