Cannot “link” other WordPress Users/Authors to Facebook

I installed and set up the Facebook for WordPress plugin. Everything works perfect. The only issues I have:

There are about three different authors in that wordpress blog. I can only link the admin user to facebook. All other authors cannot link their accounts; there is simply no popup showing up (as stated here: “Authors on your WordPress site should see a notification prompting them to connect their WordPress account with their Facebook account”). Their posts will go to de defined page though – but not the individual timelines.

The Debug page shows: “Not connected to Facebook”, yeah, that’s true – but how an I connect them?

Thanks for any suggestions

http://ww.wp.xz.cn/extend/plugins/facebook/