You can no longer use TurboTax Online to file for 2020. TurboTax Online is only for the current tax year, which is now 2021. To file for 2020 you have to use the CD/Download TurboTax software for 2020. You can purchase a download at the following link. There is no free filing for past years.
You might get a better price from a reputable online seller that still has TurboTax for 2020 in stock.
Tax returns for past years cannot be e-filed. You will have to print your 2020 tax return, sign it, and file it by mail.
You have to access your own account and/or print it for yourself using exactly the same account and user ID that you used when you prepared the return.
Many people have multiple TT accounts and forget how to access them. Log out of the account you are in now.
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 like a flash drive.
To get a copy of your previously filed returns prepared with online TurboTax https://ttlc.intuit.com/questions/1900748-how-do-i-get-a-copy-of-a-return-i-filed-in-turbotax-online
SAVE YOUR TAX RETURN !
EVERY year before mid-October you should save a copy of your tax return as a pdf and print a copy of it for your records. That way you will not be searching online frantically when you need it for a lender, FAFSA forms, your next tax return, etc.