Profootballgroup.com.au - How Does Their Discount Work?

I was at profootballgroup.com.au today trying to buy something, and the site popped up with a 30% off discount:

I thought, wow too good to be true, so I added the item to my cart and went to the checkout, where it denies my discount:

screenshots:
https://goo.gl/photos/FkZVRhbwygoQe46b6

I have contacted their support, but if they tell me to suck eggs, what other options do I have?
This seems like misleading/false advertising if their discount doesn't actually work…

Any advise? Came here partly to vent, but I would like to know who to report them to (depending on what their support staff say)
Cheers