HDFC Bank — Cashback not received

I participated in hdfc homecenter cashback offer and bought a sofa worth rs. 55960/- and was supposed to receive a cashback of 10% with coupon code hcfur20.

I applied the coupon during purchase and received relevant discount but the cashback is pending.
The purchase was made on 6th of january 2020 and the cashback isn't received even after six months which is really bad.