[Plugin: WHMCS Bridge] Not working?

Hey!

I’ve set up this plugin on my standard theme WP site.
I have configured all of the settings correctly, checked multiple times.

Nothing appears on the WHMCS, also nothing appears below the widget titles.

I also receive this error;
Error: HTTP Error:22/The requested URL returned error: 404 at http://mysite.com/billing/?systpl=portal
(I will post exact error shortly).

Thanks!

http://wordpress.org/extend/plugins/whmcs-bridge/