What version of RPG Maker MV are you using?
I'm using 1.5.1
I made this in 1.6.2, so I'm sorry to say that your 1.5.1 version can't use this plugin unless you update.
For a more technical explanation, 1.6.2 uses an updated NWJS engine which uses JavaScript ES6, ES7, ES8, which my plugin uses.
