Built-in captcha feature is enabled but it doesn't work

The built-in CAPTCHA depends on GD library (with additional FreeType support), which is an Image Processing PHP extension. Although it is installed by default on the most of the servers running PHP, it's not always the case.

The GD extension for PHP is not available
This error means that the GD library is not installed on your server. If in doubt, check your phpinfo.
Solution
Ask your hosting provider or your network administrator to install it .

The GD extension for PHP is available, but it lacks 'FreeType' support.
This error means that the GD library is installed on your server, but is has been compiled without support for truetype fonts. If in doubt, check your phpinfo.
Solution
Ask your hosting provider or your network administrator to rebuild the GD library with 'FreeType' support.

If you have no problems related to the system libraries, and you don't see any of the error messages mentioned above, but nevertheless the CAPTCHA image still doesn't appear, then the problem it's probably related to restrictions set by an .htaccess file, but often such restrictions are tricky to detect.



Additional Information
For example:

• You have a rule to disallow direct access to your /components/ directory. This rule is propagated to subdirectories, including components/com_foxcontact/lib/. You won't find the .htaccess file inside the lib directory (where the problem occurs), but you'll find it inside /components/ directory.
• A failing rewrite rule redirects your browser from the URL of the image to another page.
• If the image URL returns a blank page or the browser reports it is not a valid image format, then the captcha generator procedure fails due to a PHP error. Since this is a PHP-level problem, you should see further details in the error log of your server, rather than searching restrictions in .htaccess files.