I received the American opportunity credit last year for the first time. I am still in school but this year turbotax didn't claim it even though I'm eligble.

There's a new urban myth among college students that says they can get a $1000 from the government just for filing a tax form. For most of them, they simply aren't eligible. A full time unmarried student, under age 24, even if you don't qualify as a dependent, is only eligible for the refundable portion of the American Opportunity Credit if he supports himself by working. You cannot be supporting yourself on parental support, 529 plans or student loans & grants. You usually must have actually paid tuition, not had it paid by scholarships & grants.  It is usually best if the parent claims that credit. 

In the personal info section, when TurboTax detects that you are under age 24, it will ask if you provided more than half your support with earned income. You must answer that question YES. 

You cannot claim a credit if you are, or can be, claimed as a dependent by someone else.