If your download isn't finishing, the installer file is disappearing, or the installation is ending prematurely, check if your anti-virus is interfering. A common culprit is Segurazo / Santivirus / Segantivirus, it commonly causes installation issues and most of our users don't even know they have it installed. If you have it, uninstall it completely and restart your computer. In newer variants of Segurazo, you will need to use safe mode and use something like Malwarebytes to remove it.