I paid 12,313 for tuition and don't get a tax deduction. Why?

Are you a dependent on someone else's tax return---or are you filing married filing separately?  Those things would keep you from claiming an education credit.

https://www.irs.gov/help/ita/am-i-eligible-to-claim-an-education-credit

There are more rules for eligibility in addition to paying tuition. 

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, 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 must have actually paid tuition, not had it paid by scholarships & grants.  It is usually best if the parent claims that credit. 

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

If you are eligible, you have answered  something wrong, in the interview. But, a lot of people are just not eligible. See https://www.irs.gov/Individuals/AOTC

 or https://www.irs.gov/individuals/llc