Why won't the program prompt me to enter my SC 529 contribution?

Here is how you can enter your South Carolina 529 contributions.

1. Navigate to the South Carolina section of TurboTax (State Taxes > Your State Returns > South Carolina)
2. Continue until you arrive at the page with the heading "Here's the income that South Carolina handles differently"
3. Page down to Education
4. Select "Start" College Savings Plan Contributions
5. On the next page, report the amount you contributed to a South Carolina Tuition Prepayment Program or College Investment Program

Here is some more information on deducting 529 contributions: 529 Plans and Taxes: Deductions, Tax-Free Withdrawals & More

Where do I input a 529 deduction for New York State?

After you answer some basic questions for the New York return you'll be given a chance to make additional adjustments to federal income.  You will enter the 529 contribution in the education section. 
@BobWidman