I had this same exact problem. After looking at this conversation, I ran the install manually and saw that my McAfee Enterprise AV was stopping the install. I saw that my McAfee version was still at Patch 12. This is not compatible with Windows 10 1903. I tried to update the patch level, but that failed for reasons outside of the scope of this issue. I eventually uninstalled McAfee and then the Windows 10 upgrade could move forward.
Maybe that's the solution for others who are having trouble?
Now that Windows 10 1903 is installed, I will install a fresh copy of McAfee Enterprise Patch 13 (which is compatible with 1903).
Hopefully that helps y'all and gives you an avenue to pursue.