The most likely reason you do not qualify for the American Opportunity Tax Credit is because you are between 18-24 and do not have a tax shown on line 11 of your 1040. In order to be eligible for the refundable portion of the tax credit that would be shown on line 17c, you would have to be over 24. You are only eligible for the non-refundable portion if you are under 24.
"If you were under age 24 at the end of 2018 and the conditions listed below apply to you, you cannot claim any part of the American opportunity credit as a refundable credit on your tax return. Instead, you can claim your allowed credit, figured in Part II, only as a nonrefundable credit to reduce your tax.
You don't qualify for a refundable American opportunity credit if 1 (a, b, or c), 2, and 3 below apply to you.