For 2020, had an HSA. Contribution through work $1100, payout $1250, all medical. Should be a simple entry, but I net 0 when it's all done. What did I miss?

The HSA is handled in 3 parts in the TT program :

First the contribution:

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https://ttlc.intuit.com/replies/4785646

Next the limitations screen to confirm you are eligible to make the contributions:

Until you complete the HSA portion of the TurboTax interview to establish your eligibility for an HSA contribution, TurboTax will treat the amount entered on the W-2 form as an excess HSA contribution.

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And lastly any distribution:

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I don’t know what you mean by “netting zero”.  If you have questions about your account balance, you will have to contact the HSA bank.

On your tax return, contributions and distributions are completely separate.  If you make contributions by payroll deduction, they are recorded on your W-2 inbox 12 with code “W“.  This includes contributions you make as well as any employee match – it is all considered employer contributions because you agree to a voluntary salary reduction in the employer contributes to your account for you.  The money is already excluded from your taxable wages inbox one of your W-2.  If you make separate out-of-pocket contributions to the HSA bank directly from your own bank account, you enter those later in the program and you get a tax deduction for those contributions.

Separately, you can withdraw money to spend for qualified medical expenses. If you do not spend the money on qualified medical expenses, it is subject to a 20% tax penalty.  Because you can accumulate funds in the account over time, you do not have to spend it all in the year you contribute it, and there is no expectation that your contributions will exactly match your spending on your tax return.  On your tax return, you separately report your contributions and your spending and if you have money left over in the account, you can spend it another year.

If you don’t understand the deposits and withdrawals in your account, you will have to contact your bank.

The way that HSA tax benefits work:

1. Contributions by or through your employer.

   These are listed in box 12 on your W-2 with a code of W. The code W amount is removed from Wages in boxes 1, 3, and 5 before your W-2 is printed. 

   Thus, you do not see a deduction for HSA contributions, because they were never in your income in the first place.

2. Distributions reported on the 1099-SA.

   When you enter the total HSA distributions for the year from the 1099-SA, as soon as you indicate that all of the distribution was used for qualified medical expenses, then no tax is assessed on the distribution.

When you use the HSA as designed, you will find that you pay no tax on the way in and no tax on the way out - one of the best deals in the Tax Code.