If you were not a dependent on a 2021 tax return then you should access your tax account on the IRS website to see if the IRS has already provided you with the stimulus payment - https://www.irs.gov/payments/online-account-for-individuals
If the stimulus payment of $1,400 was not shown in your account then you need to amend your 2021 tax return that you filed and complete the Recovery Rebate Credit section of the 2021 tax return.
See this TurboTax support FAQ for amending a prior year tax return - https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-change-correct-return-a...
