Registering as a seller.

Read the page to which the above is linked. (Direct link is https://www.ebay.com.au/help/selling/getting-paid/submitting-updating-information?id=4792)

Make sure your bank account is a checking account.

Don't attempt to enter any amounts until the microdeposits have reached your bank account, as this could cause issues with verifying your account.

Make sure that the name and details on the ID and bank account are exactly as shown in your eBay account.

But... my own opinion is if you're only going to be an occasional seller, with fairly long gaps between selling items, perhaps you should think again. As a "new" seller (as eBay defines a new seller), your money will be on hold for a minimum of 21 days... and if you don't sell regularly, that hold will continue because you'll continue to be regarded as a new seller.

Other online venues may be better for you.