This isn’t an issue of the plugin. The problem involves your core WordPress installation, or your web server configuration.
Make sure you have properly configured all the pages required by the plugin – as explained into this documentation section
Make sure you have properly configured your site’s permalinks – read here
In most cases the issue can be fixed by simply going in “Settings -> Permalinks” and re-save your permalink settings. The issue is usually caused by the activation/deactivation of a new theme/plugin on your site.
Possible other causes
- apache II mod_rewrite module is not being loaded by your web server.
- Your WordPress .htaccess file is missing or not writeable by the web server.
- Apache II is configured to disallow overrides by your .htaccess file.
- First make sure that mod_rewrite is installed and enabled on your Apache II web server, and also make sure that the webserver allows your .htaccess file to override the server directory configuration.
- Make sure that your WordPress .htaccess file is present in your WordPress installation. If it is not, simply create a blank file called .htaccess and upload it to your WordPress installation folder.
- Set permissions on your .htaccess file that allows your web server to write to the file – CHMOD 666.
- Go back and set your permalinks option to the “default” option and save the change. Then set it to something other than the default and save the change.
- If your .htaccess file is writeable by the web server, it will contain new directives that sets rewrite rules for your custom permalink option.
- If it is not writeable, you will see a message below your permalinks screen that contains the rule set you need to add manually into your .htaccess file, save it, and upload it back to the WordPress installation folder.
- If the issue persists, contact your web host support team for further assistance.
For additional information on working with permalinks in WordPress, visit the WordPress Codex