I completed form 8917 for my tuition last year. This year it says I'm not eligible because there were no net qualified education expenses. I paid $15k in tuition. Why?

You not eligible because form 8917 was eliminated for 2018. That is, the Tuition and fees deduction (TFD)expired at the end of 2017.

Try this: type> letme <in the find box.  Then click jump to. That should allow yo to choose an education credit. If that doesn't work, you'll have to re-navigate the education interview