Hi Dave,
your problem is that the URL /TessContact is not managed by Joomla!, but is Apache that send you error response.
ReDJ normally is able to intercept all Joomla! calls. If you want to intercept ALL the call you need to tell to Apache to send all wrong requests to home page of Joomla! (where ReDJ can work).
This is done simply enabling .htaccess file that you can find on the root folder of your Joomla! installation (be sure your Apache has mod_rewrite enabled). Than you must add a line at the end of this file like this:
ErrorDocument 404 /
If your site is not on the root folder you need to replace the "/" with your path (e.g. /myblog). See ReDJ istructions in item page to see which is your correct line.
Hope this helps. Please, let me know if it works.
Regards,
Luigi