I'm having the same problem with a TurboTax Business return.
It could not read my prior year return, so I started 2020 from scratch. I saved it and came back to it later, but couldn't open it - got "Looks like your tax file is corrupt" message.
I created a new return one more time, got farther along - then saved and quit to see if I could open it again. Nope - got the same "your tax file is corrupt" message.
