You are registered in Australia, but you are currently signed in to ebay.com and you are posting on the ebay.com discussion boards.
You may want to sign out here and sign back in to ebay.com.au instead. Use the Help link at the bottom of the page there to request a call back or to chat with an agent.
It is only necessary to add an item to your cart if you intend to purchase multiple items from the same seller and you need to combine shipping or request an invoice.
If you are just buying single items, you should be able to purchase directly from the item page.
The cart system seems to work most consistently when the cart is kept empty until you are ready to make a purchase. Try emptying your cart and starting from there.
