If the Screen Reader worked previosly and now stopped working or if the Screen Reader doesn't produce any sounds when clicking on the 'Play' button, ensure to have installed the latest release 3.10 and to have switched to all audio engines available under plugin settings such as 'Virtual Speaker' or 'Responsive Voice'. Google Translate changed the usage terms of the free service as of December 2015 and that could be the problem causing missing audio.
If you have already installed the latest release of the plugin, the problem could be due to a file access blocked on the server. Indeed the Screen Reader scripts need to directly query a file inside the plugin folder named 'proxy.php'. Some htaccess or hosting provider rules could block direct access to files that are not the main index.php one.
In this case ensure that the htaccess is not blocking direct access to files and eventually check with the hosting provider if this is allowed.
Finally ensure that the PHP settings on the server are allowing remote socket connections, the PHP Curl library and 'allow_url_fopen'/file_get_contents.