Unless you deleted the .tax2020 file it should be on your computer. If it does not show up automatically after the "Begin" screen then use the blue "find my tax return" link and point TurboTax to the file.
https://ttlc.intuit.com/community/tax-data-file/help/find-your-tax-data-file-in-mac/00/26206
You can also use the Finder search box and search for "tax2020" on the entire computer.
If you cannot find it then you either deleted it (or the folder that it was in) by mistake so unless you have a backup copy, it is gone.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
