The coupon states Save $1.50 off 1 Colgate Pro Sensitive Toothpaste. So make sure you are buying the one that states Pro, not just Sensitive.
I have seen customers purchasing the wrong toothpaste and still using that coupon. You are wondering why that coupon is beeping, simply because you are using incorrectly. You may not know you are and that is why i am posting this message. I also do not know if anyone from my site has used it in correctly but thought i would pass along the information.