Theme Manager is just a composite front end for multiple programs. You don't need it at all, it's just a convenience (when it works properly) or a head ache when it doesn't. 
Stardock has a trial version for all it's software. They are either time-limited or function-limited depending on the individual program. I recommend WindowBlinds as the first, most important, program to get setup. it's the foundation of a full theme. After that you can add other programs for other parts of the thrme such as DeskScapes ( a personal favorite) that allows animated wallpapers, Icone Packager to change all your icons at one time, and CursorFX to use some amazing cursors.
ObjectDock is also amazing from a functional and customization stand point. And Fences will become a must-use piece of software once you see what it can do.
As for your WB problem, I'd recommend uninstall WB, reboot your computer, download the trial from stardock's site, and reinstall from there. You can grab it from here: https://www.stardock.com/products/windowblinds/
and here is a link to all their software: https://www.stardock.com/products/
welcome to the community. Hope this was helpful.
