If I've already graduated from college last year, why does TurboTax claim I still qualify for the American Opportunity Credit? I can't file taxes because of it.

It sounds to me like you missed answering some questions.   You should go back and review that you answered everything.   In TurboTax Desktop check out the following:

1. Go back to the Federal Section
2. Click into the Deductions and Credits
3. Scroll down to Education
4. Click the Visit All or Update next to Scholarships, student loans, tuition (1098-E and 1098-T)
5. On the next screen answer Yes
6. On the next screen answer both No
7. Click Edit next to the student name
8. Scroll down to Education Information
9. Answer No to the question "Was . . . working on an Associate, Bachelor or Graduate Degree", click Continue
10. Answer Yes to the question "Alright, was . . . enrolled in a Certificate or Credential Program?", click Continue
11. Select the correct answer to the question "What was . . . Enrollment Status for 2021?", click Continue
12. Answer Yes to the question "Had  . . . Earned Four Years of College Credit before 2021?", click Continue
13. Enter the correct answer to the question about the American Opportunity or Hope Credit, click Continue
14. You are now back to the Education Summary, click Continue
15. Click "Maximize my Education Tax Break", click Continue
16. Brings you to a screen that shows the amount of your Education Credit.

@oldspice0493   [Completed Answer   3/3/2022  5:31 PM PSST]