Make sure you entered all your Income and Tax Withholding in TurboTax correctly.
Form 8959 is created for you when TurboTax determines that Additional Medicare Tax is required.
If you had Self-Employment Income in addition to W-2 income, or more than one job, TurboTax calculates Additional Medicare Tax for you on that part of your income. Or, if your employer withheld Additional Medicare Tax for you, this also creates Form 8959.
Click this link for more info on Additional Medicare Tax.
You should also mention that if someone is filing jointly AND any single W2 Box 5 is greater than $200,000 it also triggers the requirement of Form 8959. This can be found on the IRS website: 2021 IRS Form 8959
Here is the important part:
Who Must File
You must file Form 8959 if one or more of the following applies to you.