If you upgrade this plugin and nothing showing up:
1-Backup your database
2-Go to the plugin option page and note what you have in there. Write them down
2-disable wp-feavorite-post plugin
NOTE: This will reset the data you have in the admin option page for that plugin. Please read #2 above
-Go to your PhpAdmin
-Locate wpfp_options click edit
-under option_value, delete what you have in there.
Go back to the wordpress admin page, plugin and reactivate the plugin
You will have nothing in there in options, you need to enter them again -- See #2 above
Save and you are good to go.
It seems that the upgrade process is not that clean. It keeps stuff in there that will cause it not to work.
If you have custom post type and nothing is showing up on the favorite page. Please add this to:
query_posts(array('post__in' => $favorite_post_ids, 'posts_per_page'=> $post_per_page, 'post_type' => 'any', 'orderby' => 'post__in', 'paged' => $page));
All custom post type will show in there. Or if you have one, just enter the custom post type name.
Go back to the site and refresh, maybe delete your cookies, and try.. It should work.