I have downloaded and run installation file from TurboTax twice thinking that the first file was perhaps faulty. The outcome was the same. TurboTax suggest running 'manual' version of installation file but it is not available for 2018 TurboTax. I have automatic updates for my Windows 8.1 OS so the latest version of Windows .net framework should be installed, which is another possible issue suggested by TurboTax.