There is no such thing as an upper age limitation to take either education credit ... you can be 100 and still qualify. You could be too young ... if you are a full time student under the age of 24 and a dependent on your parent's return you cannot get an education credit ... that credit goes to the parents.
Now what could have happened is that you used the AOTC 4 times already so you can claim the LLC instead which is something the IRS said you could do if you wanted ... I would amend the return to take that other credit ... something is better than nothing. If that is the case this is a user entry error for answering the question in the interview wrong and nothing covered by the Accuracy Guarantee.
