This message comes from the IRS Servers, not the TurboTax program. Once a social security number is "used" in the e-File system, another return containing that social security number cannot be filed. There is no workaround. You will have to print the return and mail it.
The most common reason for this to occur for tax year 2019 is when a taxpayer has incorrectly filled out the nonfiler form for the economic impact payment ("stimulus check") previously.
Other reasons can include being listed as a dependent of another taxpayer or, occasionally, identity theft.
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