I think you are referring to the screen that asks if there are any non-deductible contributions to your traditional IRA account:
First you enter your IRA distribution information and answer questions about it. Then you come to the summary screen that says Your 1099-R Entries. You need to continue on past that screen to the the screen referenced above. Maybe are you stopping when you see the summary screen so you don't see the non-deductible contributions screen?