Well, then you installed it incorrectly which is the same as not being installed at all.
Don't take this personal, but I'm going to hold your hand a bit here. Stay with me all the way regardless of how stupid you might think this is or that "you've already done it" already.... just do as I ask... I'll explain in detail:
You may have installed the mod but you did something else afterwards
OR you placed the mod's files in the wrong place. It's obvious from your issue that some or all of the mod's VN script files have either been overwritten by some other script files (some or all of the mod's VN code is missing now)
OR are not in the proper folder hierarchy.
I know my code, I know this "error" you are receiving, and I know you are not the first person to have screwed the pooch on this installation process (again, stay with me here).
Easiest resolution: start the install in a different directory as a test.
- In a newly created directory install a fresh copy of the VN.
- Place the contents of the mod's zip inside that new VN installation's "/game" folder.
- Done.
Step 2 is important. I know this sounds trivial but cut out your most likely screw up, and extract the mod's zip to a temporary spot (like your desktop)
FIRST, then copy all of those contents into the VN's "/game" folder. This will mitigate you extracting the zip file incorrectly as that is likely the cause of your initial problem.
Otherwise just post a thumbnail of your current installation's "/game" directory in file explorer and I'll tell you exactly what's wrong. Your call.