NPM SASS编译问题-POSTSS错误

我正在尝试为CSS/SASS文件集设置我的第一个构建过程。我正在学习一门在线课程，该课程运行良好，但在我的第一个实际应用程序中，PostSS模块出现了一个问题。它似乎安装正确，但运行npm run时生成脚本找不到命令（错误：找不到模块“postss”）。我运行了npmi-gpostscli，它似乎已经正确安装。编译：sass创建style.comp.css文件时没有问题，该文件是POSTSS调用的源文件

下面是package.json文件：

  "name": "campgrounds2",
  "version": "1.0.0",
  "description": "CampgroundsLive2",
  "main": "index.js",
  "scripts": {
    "watch:sass": "node-sass sass/main.scss css/style.css -w",
    "devserver": "live-server",
    "start": "npm-run-all --parallel devserver watch:sass",
    "compile:sass": "node-sass sass/main.scss css/style.comp.css",
    "prefix:css": "postcss --use autoprefixer -b 'last 10 versions' css/style.comp.css -o css/style.prefix.css",
    "compress:css": "node-sass css/style.prefix.css css/style.css --output-style compressed",
    "build:css": "npm-run-all compile:sass prefix:css compress:css"
  },
  "author": "Rick Rose",
  "license": "ISC",
  "devDependencies": {
    "autoprefixer": "^10.0.1",
    "concat": "^1.0.3",
    "node-sass": "^4.14.1",
    "npm-run-all": "^4.1.5",
    "postcss": "^8.1.1",
    "postcss-cli": "^8.1.0"
  },
  "dependencies": {}
}```