Please supply this information in a support ticket to the Tableau Support team at https://support.tableau.com
There is a newer version of Prep that has been released. Are you still experiencing this issue?
The problem is solved. I was using an app called "Duet" on my iPad. Duet allows the iPad to be used as a second monitor on my laptop. Apparently Duet prevented Tableau Prep from running. Tableau worked fine with Duet. Even if Duet was not running, Tableau Prep failed to work. Had to completely uninstall Duet for Tableau Prep to work. Making it extra difficult to identify, I was able to run Duet on a second laptop and Tableau Prep ran fine on the other laptop. Both running Windows 10.