I really think plugin author (monkey0506) must specify those requirements, because he should know better what did he use to compile them with.
Anyway, according to dependency walker, following dlls are required for that plugin to work:
MSVCP140.DLL
VCRUNTIME140.DLL
According to what I find in the web, "140" is a version of Visual C 2015. So they probably need that.
There may also be the problem, though, that there are different "sub-versions" of VC2015. At least that was true for VC2008 which is required for AGS Editor: we found that not very VC2008 matches, but one very precise package version, which we now include into AGS installer.
If you won't be able to find out why people who have VC2015 installed still cannot run the game, you may try following solution: uninstall all the visual C redistributables you have on system and reinstall them again step by step, checking whether your game works.
Of course, it is safer to do things like that on virtual machine, if you can make one.