YatraGenie — Cashback coupon invalid

Address:

Hyderabad, Andhra Pradesh, 500083

I made the journey from HYD to BBS on 1st Oct. this year and I got a 169/- cashback discount coupon with a validity of 6 months for my next booking. However, I have been trying to book 3-4 times on multiple occasions using the coupon. But why it says the coupon is not valid?? Everytime I got the reply from their customer care executive that the coupon is activated, whereas it is not