There is a carve-out for the American Opportunity Credit, it is not a TurboTax error. As the student, you can still claim this credit, even if you can be claimed as a dependent, as long as no one actually claims you. As @JillS56 said, if you are a dependent on your parents' return, then the credit can only be claimed by your parents. If their incomes are too high to claim it, then no one can claim the American Opportunity Credit.
Some families with incomes too high to claim the American Opportunity Credit for themselves may actually see a benefit in not claiming their child so the child can claim the credit. If you are considering this, be sure to consider both your federal and state tax returns, as the state may offer additional benefits for the parents claiming the child above the $500 other dependent credit that is allowed on the federal return.
