I filed and inputted everything, but as I go to pay, I noticed that the $15 dollar discount offered for being under 25 is not present. Do I need to put in a coupon code?

I made sure my birthday and everything was correct, and even went through the whole process a second time to see if it was a fluke, but the discount was not present when I went to pay. Am I missing something that makes it so I am not eligible?