Does a self -employed realtor qualify for the QBI deduction?

Yes, if you are a self-employed realtor, you qualify for QBI

"A5. A qualified trade or business is any trade or business, with two exceptions:

1. Specified service trade or business (SSTB), which includes a trade or business involving the performance of services in the fields of health, law, accounting, actuarial science, performing arts, consulting, athletics, financial services, investing and investment management, trading, dealing in certain assets or any trade or business where the principal asset is the reputation or skill of one or more of its employees. This exception only applies if a taxpayer’s taxable income exceeds $315,000 for a married couple filing a joint return, or $157,500 for all other taxpayers
    
2. Performing services as an employee" https://www.irs.gov/newsroom/tax-cuts-and-jobs-act-provision-11011-section-199a-qualified-business-income-deduction-faqs

TT isn't calculating this for me. My line 9 on the 1040 is zero. What have I missed?

What is on line 10 of your 1040 and line 12, 27, 28 and 29 of Schedule 1?  Do you have a profit?

27, 28, 29 are blank. Line 10 is 87,324 Line 12 is zero.

27, 28, 29 are blank. Line 10 is 87,324 Line 12 is zero.

If line 12 is 0 then you have no income from business so you wouldn't qualify for the deduction.  The deduction is 20% of your Qualified business income.