The aquarium has the worst ticketing system I have ever used. You don’t just use a discount code. You need to search for a promo group, select the tickets in that group, then use your additional code from there to make the discount stick.

Also, the initial search for promo groups isn’t available on mobile. If you’re buying your tickets on the way you need to request the desktop site so you can find it.

It’s also the Commonwealth Bank’s fault. If they’re trying to push these Yello rewards so hard they should make sure everything works first