I filed an extension for 2023, and It won't show the tax return that was mostly completed

You need to use the exact same account and user ID that were used when you began working on the return:

Many people have multiple TT accounts and forget how to access them.  Log out of the account you are in now.

Account Recovery

https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-online-user-id-or-password

https://ttlc.intuit.com/questions/1901486-how-many-turbotax-accounts-do-i-have

Or did you use the desktop version of TurboTax?  If so, the files are on your own hard drive or any backup device you used lik

To access your current or prior year online tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Do you have more than one TurboTax account?

See this TurboTax support FAQ for how to view all of your TurboTax accounts - https://ttlc.intuit.com/turbotax-support/en-us/help-article/account-management/many-intuit-accounts-turbotax/L9aVfKS1Z_US_en_US?uid=ll5g6zcx