The first place you will want to check for errors is your Facebook Doctor page, located on your Home screen. 

This will give you the status of your permissions with Facebook, as well as any error messages coming from Facebook. 

You can also check for errors on your Listings page, under the Manual tab.  Find the item on the Listings page.  Next to where it says where the item is queued to post, check for a red error message.  ex. Facebook error.  If you hover over this error message, a box will appear with a description of the error.

Your error messages will also appear on your Customer View page (the claim page for the item).  Go to your Manual Listings page, find the item on the table, then click the silhouette icon, or Customer View, under the Tools header.  Scroll down and it will list where the item has been listed, as well as any error messages you may be getting kicked back.  

Common error messages: 

'post' error: [368] It looks like you were misusing this feature by going too fast. You’ve been blocked from using it.

'post' error: [190] Error validating access token: Session does not match current stored session. This may be because the user changed the password since the time the session was created or Facebook has changed the session for security reasons.

'post' error: [100] Unsupported Post Request. Object with ID " " does not exist, cannot be loaded due to missing permissions, or does not support this operation."