Maryland does not tax social security, even if it is taxed on your federal return. Maryland does, however, have a pension exclusion "deduction" that considers how much social security you receive. If you have a pension other than social security, when you entered your social security the amount of pension taxed would have increased by the same amount.
If your social security (SSA-1099) was properly entered in TurboTax, and any portion is shown as taxable (line 5b of Form 1040), check the "subtractions" on your Maryland return. You should see any federally taxable social security deducted there.
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