2019 Premier should be able to open any *.tax2019 data file. However, if the data file has a state return in it, then you had to download the state program into your TurboTax before opening the file, or it produces an Error 190. Without the state program it doesn't know how to handle the state data present in the *.tax2019 data file.
You say you have now downloaded the 2019 California state program into 2019 Premier. Did you then close TurboTax and restart your computer?
If not, try that first.
The FAQ doesn't mention that step, but I've found it can help some users after downloading state.
@jyeh74 ADDENDUM 2/16/21 at 6:27 PM Pacific
Also see my comment I left you below about being sure your 2019 CD version of Premier is up to date. Hopefully, you updated the software after installing the program.
