It's not shown on github but if you use the plugin download link you will see the dependencies folder has a subfolder called "LoudnessTextFiles"
There is nothing in this folder, it's used as temporary storage. If it's missing the plugin will complain. So you just need to create a new folder in the dependencies folder you copied during install and call it "LoudnessTextFiles".
I haven't tested the plugin so no idea if it works but that should solve your current issue.