You can check for errors on your inventory page, under the manage tab. Next to where it shows the links, you may see a grey triangle error message.  If you hover over this error message, a box will appear with a description of the error.

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."