Go through and select to EDIT your business income and expense entry section again, even though you may not make any changes to see if that will trigger the calculation. Plus double check the QBI questions asked after you say you are "done" entering any Schedule C activity.
Note that there are threshold levels that impact the QBI calculation depending upon the type of business income, plus not all rental activity is eligible for the deduction.
Below are steps to preview your 1040 form before filing your taxes in TurboTax online:
https://ttlc.intuit.com/replies/3302322