EDIT: I fixed the problem by uninstall and reinstalling turbotax.
I'm having the same problem. I tried your solution to start a new return then go to state and download. Same problem. It doesn't look like its downloading my California state but it says it did and will not let me continue.
I also did the repair option under uninstall. that didn't work either.
Im on windows 10.
This is TurboTax deluxe and state 2019