There is a serious bug in the latest version of the plugin, where a post is always published to the user's profile page rather than a select fan page. Luckily, I've managed to isolate the issue and put in a fix.
On line 308 of fpp_index.php, look for:
$api_url = 'https://graph.facebook.com/me/links';
and replace it with:
$api_url = 'https://graph.facebook.com/'.$object_id.'/links';
This will fix the issue for anyone experiencing the same problem.
Hope this will be added as a permanent fix to the next release.