eBay will see you as a "new seller" since you haven't sold for over a year. You must also register and be verified for Managed Payments as sellers can't use Paypal anymore for selling. If you haven't got your Managed Payments sorted out that could well be why you're having trouble listing.

https://www.ebay.com.au/help/selling/selling/start-selling-ebay?id=4081

https://www.ebay.com.au/help/selling/getting-paid/registering-seller?id=4792