The Qualified Business Income Deduction is not a straight 20% off your self-employment income as there are several pieces to how the deduction is calculated, plus there are thresholds and business types that may reduce or eliminate the ability for the deduction.
But, the first thing to check is whether you have downloaded all the available software updates for TurboTax as there may have been updates completed recently that relate to the deduction.
The Qualified Business Income Deduction is reported on line 9 of the 1040, so after downloading the most recent updates, check your 1040 form to see if you see an amount on line 9. Here is how to get to Forms Mode within TurboTax -- once there click on 1040 form on the left side of the screen to see your 1040 return.
https://ttlc.intuit.com/replies/3339204
Here is more information on how the Qualified Business Income Deduction is calculated and who is qualified to deduct it:
https://ttlc.intuit.com/replies/7019998
Turbo Tax 2019 is not calculating the Qualified Business Income Deduction on my 1040 from my 1065 K-1 even though I meet all of the requirements. It is very frustrating to be stuck in this situation and no human being to talk to why it has this flaw and how to fix it.