Hi
It is the weekend - I am sure that they will respond on Monday if you have an account with them.
Are these the instructions that you are following?
1. Install the S5 Box module and publish it to all pages on your site. Try to publish it to a position where a module already exists on all pages, but don't worry it won't change the layout of your site, the script is automatically hidden on your site.
2. Install and publish the S5 Register module to the 'register' module position
3. Publish the default Joomla login module to the 'login' module position.
4. In your template parameters area of Joomla you can change the text for login, register and logout.
5. That's it, you're all done!
For 1. have you published to all pages and in a position where a module already exists?
Regards