Are you using your .tax2019 file? To transfer your 2019 information into your 2020 return, start a new return, when it asks if you want to transfer your 2019 return select the file your want to transfer (.tax2019) or if your return is not showing in the box area, browse to where you saved your 2019 tax file.
You cannot open your 2019 return into the 2020 software, you can only transfer your 2019 information.