You can’t get the refundable portion if you haven’t had enough earned income to provide more than half of your support and have a living parent. If you are a dependent it’s generally better that the parent claim that credit if otherwise eligible.
The usual reason for that is that you have indicated that you can be claimed as a dependent on somebody else's tax return (usually you parents) and that they are not actually claiming you and/or you are a full time student, under 24 who does not provide more than half their support with your own earned income.
While technically there is a provision that allows your student-dependent to claim a federal tuition credit, from a practical matter it seldom works out. A student, under age 24, is only eligible for the refundable portion of the American Opportunity Credit (AOTC) if he/she supports himself by working. She cannot be supporting herself on student loans & grants and 529 plans and parental support. It is usually best if the parent claims that credit.
If the student actually has a tax liability, there is a provision to allow him to claim a non-refundable tuition credit. But then the parent must forgo claiming the student as a dependent, and the $500 other dependent credit. The student must still indicate that he can be claimed as a dependent, on his return. This is worth up to $2500 (AOTC shifts to all non refundable)
https://ttlc.intuit.com/questions/3936383-tuition-gift-to-children