I agree that TurboTax has a glitch. I think your line was blank because they were taking the $1300 and subtracting $1400 in error, which left a negative amount, so it just was blank.
I have a similar issue, but received $2292 recovery rebate credit as part of the 2020 Federal refund in 2021. I believe the $2292 should be removed from my federal refund for line 27, because it was really a "late stimulus payment". However, TurboTax isn't subtracting the $2292 but is subtracting the $5600 rebate credit that should not be removed because it was never in my Federal Tax Refund number.
I hope someone from TurboTax looks into this issue and corrects it. I am going to reach out to Iowa Department of Revenue to understand what number to put in the form and override. Thank goodness for Desktop version.
