The CSS is not loading correctly, you've not provided CB or Joomla versions either. Have you tested with debug mode enabled and maximum error reporting from within Joomla global configuration? Please see the help us help you FAQ at the below link, more information is needed.

www.joomlapolis.com/support/faqs

This is in response to your original thread, you HAVE the buttons, but you've something installed that is messing with the CSS.

Please PM backend login credentials and will take a look.

Have reviewed your installation and there was a number of issues. First you had a JS and CSS compression extension installed, extremely bad idea. I've disabled this system plugin CssJsCompress. This will corrupt ALL CSS and JS, suggesting you uninstall it.

Next you had the caching system plugin enabled, but caching disabled. This causes massive overhead to your site and for it to render cached inaccurate information. I've disabled the system plugin cache. This will disable all caching as site based caching is NOT recommend. The only cache you should ever use should be server side.

Finally you've a known conflict, poorly written, CB video plugin called cb.video. I've disabled this to eliminate it's fatal JS error.

With the above done I can see and use the FBC button perfectly fine with the message as follows.

"Your registration is not confirmed yet"

I receive the above because you have FBC configured to use CBs admin approval setting, which you've registrations to require approval so is behaving as expected. User will understand what is going on however as they receive the above message. It of course can't log them in with this configured. Edit FBC via parameters to disable admin approval for FBC users if you like.