As stated by expert DanaB27, the distribution must be from an IRA, the distribution code on Form 1099-R must be '7', and the IRA/SEP/Simple box must be checked in order for TurboTax to recognize that the distribution may qualify as a QCD.
Otherwise, without that box being checked, the distribution is treated as a retirement plan distribution, not an IRA. Retirement plans other than IRAs are not eligible for the QCD tax treatment.
If the box is not checked, you need to request a corrected Form 1099-R from your IRA custodian in order to receive the correct tax computation on your return.