yarn run devでBrowser Syncが動いていない？

環境・状況
Mac High Sierra 10.13.6
Visual Studio Code使用
Google Chrome使用
Firebase Hostingのプロジェクトディレクトリ内に以下のように配置
.
├── public #納品対象
│ ├── css
│ ├── font
│ ├── image
│ └── js
└── src #開発
├── css #.scssを格納する
├── font
├── image
└── js

概要
当方デザイナーですが、FEからgithubでソースをゆずり受け以下をターミナルで実行

$ yarn run dev

localhost:3000が自動で立ち上がりブラウザに「Browser Sync」と表示がされていたので、ちゃんと動いているかと思ったのですが、Visual studio Codeでcssやhtmlを保存してもChromeに自動反映されません。。。

Package.json
1"dependencies": {
2    "autoprefixer": "^9.2.1",
3    "browser-sync": "^2.26.3",
4    "chokidar-cli": "^1.2.1",
5    "concurrently": "^4.1.0",
6    "cpx": "^1.5.0",
7    "imagemin": "^6.1.0",
8    "imagemin-gifsicle": "^6.0.1",
9    "imagemin-keep-folder": "^5.3.2",
10    "imagemin-mozjpeg": "^8.0.0",
11    "imagemin-pngquant": "^7.0.0",
12    "imagemin-svgo": "^7.0.0",
13    "inline-css": "^2.4.1",
14    "juice": "^5.1.0",
15    "node-sass": "^4.9.4",
16    "node-sass-chokidar": "^1.3.4",
17    "node-static": "^0.7.11",
18    "nodemailer": "^5.1.1",
19    "npm-run-all": "^4.1.3",
20    "postcss": "^7.0.5",
21    "postcss-cli": "^6.0.1"
22  },
23  "scripts": {
24    "build-sass:autoprefixer": "postcss --use autoprefixer --no-map --replace \"public/**/*.css\" ",
25    "build-sass:scss": "node-sass-chokidar src/ -o public/ --output-style compressed",
26    "build-css": "npm-run-all -p build-sass:*",
27    "dev:watch-css": "yarn run build-css && chokidar 'src/**/*.scss' -c 'yarn run build-css' -p",
28    "build-copy": "cpx \"src/**/{*.html,*.eot,*.svg,*.ttf,*.woff,*.jpg,*.png,*.js}\" \"public/\" -C",
29    "dev:watch-static": "yarn run build-copy && chokidar 'src/**/{*.html,*.eot,*.svg,*.ttf,*.woff,*.jpg,*.png,*.css,*.js}' -c 'yarn run build-copy' -p",
30    "serve": "browser-sync start --server ./public/",
31    "dev": "concurrently \"yarn run dev:watch-static\" \"yarn run dev:watch-css\" \"yarn run serve\"",
32    "imagemin": "node imagemin.js",
33    "build": "yarn run build-css && yarn run build-copy && yarn run imagemin"
34  },
35  "browserslist": [
36    "last 2 versions",
37    "not ie < 10",
38    "Android >= 4",
39    "iOS >= 9"
40  ]