The "run as Administrator" worked for me, thank you for posting!
Also note that if the install is "stuck" because the installer is already running, open Task Manager, go to the Details tab, find "msiexec.exe" and click End Task.
It appears to me to that this is a bug that Intuit should address, since I am running TurboTax 2018 on the same computer with the same account and it updated without any problem. At a minimum, if the install is going to fail due to not running as an Admin, it should provide a clear error message and not just fail without an explanation.
