If I am remembering correctly Turbotax references your previous years tax return to allow you to use the software to files your new year's return. I filed an extension and I am wanting to use Turbotax to file my 2021 federal return.
You don't have to transfer from 2020. You can do 2021 from scratch. How did you do 2020? You can try to transfer from a pdf file or another company's file. Transfer pdf to Online version. See the section if you used other software last year.
https://ttlc.intuit.com/community/entering-importing/help/how-do-i-transfer-last-year-s-return-into-turbotax-online/00/25953
BUT you only have a couple days to use the Online version and efile. Online closes on Oct 17. If you have to finish after that you need to use the Desktop CD/Download program on your computer and mail your return.
Start an Online return here,
https://turbotax.intuit.com/personal-taxes/online
Or buy the Desktop CD or the Download program here,
https://turbotax.intuit.com/personal-taxes/cd-download