Browsing Amazon.com.au on PC and saw a note under some products "Get $10 off only on Amazon Mobile App"
I signed in on the Android App, went to the product, clicked redeem offer, and it applied $10 discount in cart.
Here is the link with more details https://www.ozbargain.com.au/node/658341
The same deal was listed here but is closed and expired. But it's working until 30-Nov
Promotion terms
These terms and conditions apply whereby any existing customer of amazon.com.au who has not previously made a purchase through the Amazon App (Australia store) and has either been invited from Amazon or who has clicked through on site marketing whilst signed into their Amazon customer account, is eligible to receive $10 off their first purchase of over $39 of “eligible items” made on the Amazon App (Australia store) only ("offer"). For the purpose of these terms and conditions "eligible items" refers to any product shipped and sold by Amazon AU on the Amazon app and excludes products sold by third party sellers (even if fulfilled by Amazon, or sold by Amazon US), digital purchases such as e-books, subscriptions such as prime video and audible, gift cards and postage or delivery rates. Amazon's standard delivery rates and policies apply to any purchase made pursuant to the offer. To redeem the offer, visit https://www.amazon.com.au/b?node=7293361051 and follow the instructions to redeem. Once you have added at least $39 of eligible items to your cart, your $10 total discount will be automatically applied to eligible items at checkout. If you do not add any eligible items to your cart, the offer will not apply. If you return any item purchased using the offer, Amazon will only refund the price actually paid for the item (that is, less the value of the offer) and the offer will be invalidated. The offer is not transferable and may not be resold. This offer cannot be used on pre-existing orders or orders placed with 1-click. If you violate any terms and conditions of the offer, the offer will be invalid, and the discount will not apply. This offer cannot be used in conjunction with any other offer or code for new customers or Amazon devices. The offer is subject to availability and Amazon reserves the right to cancel, amend or withdraw the offer at any time at its discretion. Amazon.com.au’s Conditions of Use and Sale apply. The offer is valid until 23:59 (AEST) on 30 Nov 2021 unless withdrawn earlier.
Not sure why it doesn’t work for me, this is my 1st app purchase for Red Dead Redemption 2 ps4 $39, it says The promotion code you entered cannot be applied to your purchase 😢