This is a typical scenario when you leave a software there from over 7 years ago, (with installation issues of 7 years ago) and then you install the modern alternative.
God knows what that un-installation left behind.. It was not designed to be uninstalled NOW against modern OS with Latest updates. (unless your OS is also archaic). In that case make sure you install latest updates for the new version at least.
V12 was designed to be uninstalled round about year 2014.
So when you remove a software like this, late (like years later) then please run a sanity check and restart this OS between installations.
Update the thread of the post to something like this:
I uninstall V12. I install V15, Services do not start.
That sound much fairer