If booking fails, immediately mail infinia support on hdfcbank as well as smartbuy. Usually they follow up. Had OTP problem and they as it showed "failed" on order history. Even once in hotel booking I had name change. They followed up for same. Flight cancelled by indigo, they confirmed I'll get full refund. Dunno about taxes part.
Also, I always say, use hotel booking to EARN points. Flights or tanishq to REDEEM them.