Hey there! Let's walk through the most common reasons why some of your Font Awesome 4.7.0 icons aren't showing up, even after trying different CDN links:

• The icon doesn't exist in Font Awesome 4.7.0
  Font Awesome adds new icons with each version, and some icons you're trying to use might have been introduced in 5.x or later (especially many brand icons). Double-check the official icon list for 4.7.0 to confirm if your target icon is included. If it's a newer icon, you'll either need to upgrade your Font Awesome version or find a suitable alternative from the 4.7.0 library.

• Incorrect icon class names
  Class naming changed significantly between 4.x and 5.x. In 4.7.0, all icons use the base class fa followed by the specific icon class (e.g., fa fa-star). If you're using 5.x-style prefixes like fab, fas, or far, those won't work with 4.7.0. Make sure you're using the exact class names specified for the 4.7.0 version.

• Browser caching issues
  Your browser might be holding onto a cached, outdated or corrupted version of the Font Awesome CSS file. Try forcing a hard refresh of your page: press Ctrl+Shift+R (Windows/Linux) or Cmd+Shift+R (Mac). You can also add a query string to your CDN link (e.g., https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.7.0/css/font-awesome.min.css?v=4.7.0) to prompt the browser to fetch a fresh copy.

• CSS conflicts or priority issues
  Custom CSS or other stylesheets in your project might be overriding Font Awesome's styles. For example, a rule that sets display: none on the icon element, or changes the font-family away from 'FontAwesome', can break icon rendering. Use your browser's developer tools (F12) to inspect the problematic icon: check the "Applied Styles" tab to see if any styles are overriding the default Font Awesome rules. Ensure the font-family property includes 'FontAwesome' and the pseudo-element's content value matches the expected icon code.

• Failed CDN resource loading
  Even with a valid CDN link, network restrictions or temporary outages might prevent the CSS file from loading. Open your browser's Network tab (in developer tools), refresh the page, and check if the Font Awesome CSS file loads with a 200 status code. If it fails to load, try downloading the Font Awesome 4.7.0 files locally and linking to the local CSS file instead (e.g., <link rel="stylesheet" href="./path/to/font-awesome.min.css">).

内容的提问来源于stack exchange，提问作者dylanhibbert1