I actually have the exact same problem as you do, can I ask you what exactly that you did to fix it?
I also do the same uninstall the patch, still can't, reinstall the whole thing, still same. what can I do to fix this?
I tried doing the same you mentioned, installing Klite Codec, basic, did nothing, Mega did nothing as well, the app still doesn't open, only exist as a background process as Nexas but no open window.
anyone find a reason for this? am I stuck on being unable to install Majikoi S in this computer?