A number of things could have gone wrong. such as, reservation not properly attached to ticket. This is not unlikely since I assume it's a paper ticket.

Until a couple of months ago, both the web booking and reser4vation check things seemed to be very inconsistent. As of late, though I have had a 100% success with both.

Might be worth checking that you can see the reservation using the "bookings" tool on Ac.com.