This is for TT 2020 version. I saw another post that recommended uninstalling TT and then reinstalling. I did that and it appears to have worked. I was getting the same fatal error message when I attempted to update the original downloaded version. I followed his advice and did not uninstall TT myself, but it will ask you if you want to uninstall the original TT version when you download or use the CD. That is what I elected to do and it seems to have worked and it does not appear that I lost any of my previous work... Good luck!
