Merchant doesn't honor its coupons

We went to dinner at Wheelhouse Tavern. We have an entertainment book coupon worth $24 off a dinner entree any day of the week. After the bill came and we tried to use the coupon the waitress said they don't take the coupon for lobster. We asked to have the coupon value $24 taken off and they said no. If we had gotten a steak they would have taken it off or something else, but the owner's were losing too much money by people trying to use the coupons so they stopped taking them without telling anyone. No signs are listed in the restaurant. It is just bad business.