Facebook doesn't recognise authorised domains

The JFBCFeed widget was removed from JFBConnect quite some time ago. For an updated list of available easy-tags, please go into the JFBConnect backend > Social > Examples tab. Then select Facebook as the provider to the see the list of FB widgets. You can also add the widgets to your page using the SCSocialWidget module by selecting the FB provider, appropriate widget type and the widget's parameters.

[Edited to add] Since you're setting up a channel and talking about test preview, it sounds like you want to use the SCSocialStream module. In that module, you'll be able to select the channel you've just created and the module will pull in that channel's posts.

-Melissa