Why 2017 turbo tax program does not give me the option to exclude already taxed NJ IRA distributions from NJ taxable income?

I converted traditional IRA to Roth IRA in 2017 and 2018. The 2018 turbo tax program allowed me to exclude the already taxed portion of the converted amount from NJ taxable income. However, I was not able to do this with the 2017 turbo tax program. I was trying to do amendment for 2017 to correct this, but the turbo tax program does not have this option. Why is this?