I tested the coupon with 2 different flights and it did give me 15% off but it was still too expensive for flights that i paid $1600 last year and now they want ~$2300. The World cup might have something to do with this but the deal might come handy for someone. Not sure of the expiry date.
Found the link with the T&Cs https://www.qatarairways.com/en-au/offers/cug/paypal.html?ci…
i tried to Europe in May, didn't get 15% discount. Have you got the T&C?