I had the same problem. I looked at the bower.json file for font-awesome and found this:
{ "name": "font-awesome", "description": "Font Awesome", "keywords": [], "homepage": "http://fontawesome.io", "dependencies": {}, "devDependencies": {}, "license": ["OFL-1.1", "MIT", "CC-BY-3.0"], "main": [ "less/font-awesome.less", "scss/font-awesome.scss" ], "ignore": [ "*/.*", "*.json", "src", "*.yml", "Gemfile", "Gemfile.lock", "*.md" ] }
There was no reference to font-awesome.css in the "main" array. Perhaps, like me, you are not using SASS or LESS for styling. Therefore, no style is added for fonts. I modified the json file as follows:
{ "name": "font-awesome", "description": "Font Awesome", "keywords": [], "homepage": "http://fontawesome.io", "dependencies": {}, "devDependencies": {}, "license": ["OFL-1.1", "MIT", "CC-BY-3.0"], "main": [ "less/font-awesome.less", "scss/font-awesome.scss", "css/font-awesome.css", "fonts/fontawesome-webfont.tff", "fonts/fontawesome-webfont.woff", "fonts/fontawesome-webfont.woff2" ], "ignore": [ "*/.*", "*.json", "src", "*.yml", "Gemfile", "Gemfile.lock", "*.md" ] }
I saved and started serving grunt, and now my font extension icons appear.
Hope this helps.