Are you missing public posts that users have been publishing to your Facebook Page? Here might be the reason and how to fix it!
Unfortunately, Facebook offers some largely unknown, quite opaque Privacy Settings to each individual user. Although not really intuitive, some of these settings also affect the visibility of public posts a user publishes on the timeline of your Page, Event or Group. The specific setting can be found here: https://www.facebook.com/settings?tab=applications:
How to fix this for an individual user?
Ask the user to check their privacy settings at https://www.facebook.com/settings?tab=applications. In "Apps others use", ask them to ensure that the option "Posts on my timeline" is activated. If this setting is de-activated, even public posts a user publishes to your Facebook Page can not be accessed through the Facebook API, and will therefore not appear on your social wall!
Please note: if users change this setting, it will only affect posts published after the change.
Grant Manage Pages Privileges
Due to certain limitations on Facebook, we cannot fetch some posts from your Facebook Page, even if they are visible on facebook.com. You can fix this for Pages for which you are an administrator. Just click the Upgrade button and grant us the "Manage Pages" privilege. Don't worry: We cannot and will never publish to your page.