Hello, I've been busy with... life and such so I'm not sure I can fix the bug.
But from my testing, it worked fine?
I've downloaded miku_fnf_21_mod.zip from here and made it search the downloaded directory and it worked on my machine.
Instead of installing, try searching the mod directory directly.
Thanks for trying out my mod.
Also, if you could copy paste the terminal output, that'd be great.