Swiggy - False Coupon

I was given a coupon after there was delay and handling of food, after numerous chats they gave me a token of apology of Rs. *** which they stated can be used at any restaurant order except domino's. I was unhappy since most times the handling of the food is very bad, but I don't blame the delivery partner as the restaurant should pack food properly. However, the coupon was valid for ** days and the complaint was on **nd Dec ****, I tried to use it couple of times but it did not work and I did not bothered but today is the last day to use it and I tried to use and it still doesn't work, after chatting to the customer care executive he wasn't able to provide me any reason and stated it technical difficulty and asked if he can give another coupon why will I need those useless coupon.