[Plugin: Mudslide Custom Errors] Plugin not working, even with error.php file

I created an error.php file and put it in my template; however, the plugin is not working.

This is the code I used in my error.php file:

<?php
echo '<br>' . $title;
echo '<br>' . $message;
?>

I put the file in the root of my active theme folder (platformbase, which is a child theme of Platform Pro).

Thanks,
Karen

http://wordpress.org/extend/plugins/mudslide-error-pages/