I checked form 8995 and Line 1 lists both businesses but has QBI=0 for this one.
turbotax shows the QBI calculations with an explanation of how the amount was determined at the end of the ionterview for the one business but not the one it decided has 0 QBI. I've revisited many times and even tried changing the business code to Misc (999000 or something.) I get the interview about SSTB but I say it is not one of those and not deriving income from one of those. The only real difference seems to be that the problem business income came on a 1099-NEC.
I don't think it matters but there's actually a third business with a very small amount of earnings that was paid with a w2. that also shows 0 QBI, but I expect that because of the w2. all businesses use my name as the business name and are cash basis.
Have you reviewed the QBI Smart Worksheet on Schedule C for the business with QBI=0? This worksheet appears after Part V and provides details on how the deduction is calculated, which appears on Line H. If you have net income for this business, some adjustment must be zeroing out the income for QBI.
@user-1253