You may want to lodge a complaint with the Office of Fair Trading in QLD. If the seller is a legitimate business, that may be your only recourse at this stage.
You may also want to contact your bank if your payment source was a credit/debit card. I don't fancy your chances with your bank, though, because your purchase was more than a year ago.
In cases like this, you need enforceable consumer protection. That means that you must rely on the item warranty, and the terms of the purchase must be such as not to negate that warranty. There's also the reasonable expectation for the item to be able to be used for a certain amount of time under Australian Consumer Law.
As has been said, a warranty by a seller on eBay might not be something on which you can rely. A great deal depends upon whether the seller is an authorised Australian dealer. Hopefully you can resolve this - but there isn't an eBay process for relying on a seller's warranty. If an item stops working after a year, only Australian consumer protection can really help you.
When buying an item where a warranty is something on which you want to rely, only ever ever ever buy from an authorised seller. You may want to check with the local distributor or the manufacturer, as appropriate, to see who is an authorised seller. Remember that if you buy from an international seller, the item will be a grey import/parallel import, and that also has certain implications in terms of warranty. Make sure you understand any of those implications and limitations.
