Are/were you the student in 2018? Were you still an undergraduate in 2018? Were you under the age of 24 on Dec 31 of the tax year? If you answered yes to all these questions, then with rare exception your parents qualify to claim you as a dependent on their tax return. That being the case, you don't qualify for any education credits at all. But then, never say never. Depending on the circumstances, there is an ever rarer instance where you could qualify for the refundable portion of the AOC if you meet exacting requirements. Not many do.
Because of age, only if you earned less than $4,150 in 2018 would your parents qualify to claim you on their tax return. Assuming you earned more than that, you may need to work back through the education section again and check your responses. Chances are high you answered one wrong. For example, there's a question that asks if "you the student" provided more than half of your own support. If you did in fact do so, you probably misinterpreted the question and answered it wrong. Keep in mind this is only an example of one possibility. It's still perfectly possible that you did not provide more than half of your own support, even if you earned a million dollars. For example, if you received $80K in scholarships, grants and 529 funds, those do not count for you providing your own support. That would be considered third party support. So with that much in 3rd party support, even with a million dollars in earned income there's no way you provided more than half of your own support.
But I digress. You need to work through the education section again and check your data. More than likely, one or more item you selected/entered is wrong. Additionally, if your income as a single person exceeds $80K for the year, then you don't qualify for any credits at all. Finally, be aware that the tuition and fees deduction expired at the end of 2017. So any out-of-pocket education expenses you may have paid with earned income in 2018 are just flat out not deductible at all.
Since he/she is over 23, the dependent support rule changes from "didn't provided more than half of your own support" to "your parents must not have provide more than half your support. That is age, alone disqualifies her from being a qualifying child, so the qualifying relative rules apply. Full rules: <a rel="nofollow" target="_blank" href="https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html">https://turbotax.intuit.com/tax-tools/tax-tips/Family/Rules-for-Claiming-a-Dependent-on-Your-Tax-Return/INF12139.html</a>
But that should be academic. His birth date, alone, will prompt TurboTax (TT) to ask the correct version of the support question.
I agree with Carl, you've answered something wrong in the interview.
You must be over age 23.
You cannot be a grad student.
You (or your parents) must not have claimed the American Opportunity Credit (AOC) 4 times in the past.
You must be a half time, or more, student
Your parents must not qualify to claim you as a dependent (not actually claiming you is not enough)
Your school must be an eligible institution.