If you were eligible for EIC the TurboTax program would have entered the EIC on your 2021 Form 1040 Line 27a. You were asked if the 2019 Adjusted Gross Income was greater than your 2021 AGI and if so you should have use the 2019 AGI to calculate the EIC.
Use the IRS assistant to verify that you are eligible for EIC - https://www.irs.gov/credits-deductions/individuals/earned-income-tax-credit-eitc
See this TurboTax support FAQ for amending a 2021 return originally completed and filed using TurboTax - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-2021-return/L1gEU4G3X_U...
