What was the time lapse between your booking and the call? Generally speaking, CX has 72 hours to confirm positive space. If it does not, AA must cancel the ticket. Generally the 72 hours is a non-issue, but if something goes wrong, it could be.
In any event, you really need to call the EXP desk (calling customer service should get you to EXP either because the system recognizes your phone number or when you enter your number). You need the specific reason why.