If you could be claimed as someone else's dependent for 2021 you were not eligible for a stimulus check. If you were eligible and did not receive the stimulus check, you could have used the recovery rebate credit on your 2021 tax return to get the 3rd EIP payment.
First check your online account with the IRS to see if the IRS shows an EIP payment for you. If it is not there, and you were not someone's dependent, then amend your 2021 return to use the recovery rebate credit in Federal Review.
https://www.irs.gov/payments/your-online-account
Make sure you have saved a pdf of the original return before you amend. (If you do not save it as a pdf, the amended return will overwrite the original, and the original will be lost forever)
See this TurboTax support FAQ for amending a tax return -
Do not expect quick results from amending. It can take four months or more for the IRS to process an amended return.
You can watch for information here:
https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1
For eligibility check: 2021 Recovery Rebate Credit Questions and Answers.
Taxpayers who qualify but did not claim any portion of the credit on their 2021 tax return should have received these payments by late January 2025. The payment were sent to the bank account listed on the taxpayer’s 2023 tax return or to the address of record.