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.
