Turbotax is not designed to upload a PDF prepared by Turbotax, only other tax providers. If you used Turbotax last year, you should upload your tax data file, or use the same online account as before. If you used a different provider and it can't read your PDF, you aren't losing very much. It still only imports basic information and not more advance details. You can prepare your 2020 return and when it needs information from 2019, it will ask you and you can enter it manually.
