jfb invite not working or showing up

I'm a little confused as to what's happening, but if you can post the URL of the page, that will likely help me to figure it all out.

It sounds like the Invite module isn't appearing. As for the Like button showing twice, it's possible you have the JFBCContent plugin enabled which shows the Comment box and like button. Strangely, the Comment button also has it's own Like button. If this is the case, edit the parameters in the JFBCContent plugin and tell it to hide the extra like button.

Hope that helps, and we'll help you figure out the Invite module when we see it.