I got this as well, when attempting to file my 2019 MO-A Form with TurboTax Online.
The State Income Tax Refund Smart Worksheet screen showed zeros for "Total State and Local Refunds from 2018" and "Remaining State and Local Refunds from 2018", so I entered a zero in "Minus any Refund from 2018 Kansas City and/or St. Louis".
I think TurboTax Online just doesn't handle local taxes as elegantly as it could, and the programmers missed this.
