The Self Employed Tax Credit was Only available for self employed persons that had a net income in tax years 2020 and 2021.
Filing for the 2020 SETC is no longer available since the 2020 tax return with the credit had to be filed on or before May 17, 2024.
If you filed a 2021 tax return as a self employed individual, were affected by Covid so that you could not work and did not file for the credit, you will have to file an amended 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...