If you are using WIN 10 then uninstalled OS updates can hang up the TT program updates ... install the WIN updates at least 3 times and then reboot the computer.   Then try updating the TT program making sure you are using an administrator account, the program is installed on the C drive  and that you don't have any removable drives in the USB ports.  

If that does not work try a manual update:

• What is a manual update?
• Where's the manual update for Mac?

IF on a Windows system, did you try checking for your Windows updates, and then rebooting?

Any  partially-installed recent Windows updates, on anyone's computer, have been known to block TTX updates from completing until the Windows update is fully installed and rebooted.  I know a Windows update was released sometime in the last two weeks.

Thanks for your reply. I'm on auto-install for Windows updates. latest Windows update was installed earlier this week, Monday or Tuesday. Yesterday I was able to open Turbo Tax 2020 after doing a normal TT update. But today could not open it even after 2 more normal TT updates. Plus two tries today using the recommended 191MB update which did ot work either .

If you are using WIN 10 then uninstalled OS updates can hang up the TT program updates ... install the WIN updates at least 3 times and then reboot the computer.   Then try updating the TT program making sure you are using an administrator account, the program is installed on the C drive  and that you don't have any removable drives in the USB ports.  

If that does not work try a manual update:

• What is a manual update?
• Where's the manual update for Mac?

Reboot your computer. If it still does not update, try reinstalling TurboTax