I have error code IND-116. Child over 17 is full time student. I understand i cannot get child tax credit for this child. How do i fix this?

Go the My Info in the left-hand menu when you're in your return (if you've just signed in to TurboTax, select Take me to my return first). Then in the Personal info summary section, remove your dependent, and then refile your tax return.

Here is also some more (general) info on fixing a rejected return:

https://ttlc.intuit.com/replies/3302275