IHOP review: Complaint about not honoring coupon

I recently had a coupon for a free stack of pancakes at the East Brunswick NJ IHOP. It was emailed to me, and said Happy Anniversary. IT was delicious. A few days later I received another email for another free stack of pancakes, this one said Happy Birthday, My birthday was 12/16. My wife and I went to the East Brunswick, and were told the coupon was used already, The server tried to validate it, and then the manager tried and said it was already used. It was not.! They would not honor it. I do not feel that this situation was handled appropriately. We would also have ordered more food than the coupon was worth., so they would have made a profit on us. We have been going to IHOP restaurants since the 1970's. I do not think that was right. Charles Manfre 18 Cosgrove Court East Brunswick NJ [protected]