We do make multiple attempts to deliver the content, but if you’ve received this message it means we’ve ultimately been unsuccessful.
If you tend to send the same type of message (i.e. always using a link, a photo, or a keyword), or you tend to send at the same time every day and to a lot of profiles at the same time, Facebook may identify that repeated activity and begin to limit those types of posts.
We recommend varying your content and the timing of your posts so that these don’t appear to be automated. That should help with content posting more reliably.
Otherwise, Facebook does experience hiccups from time to time, so try copying the content of the post and try re-sending immediately.
Unknown Twitter error
We’re sorry for the inconvenience, but your tweet: [Tweet Content], sent from your profile: [Profile Name], did not post due to an unknown Twitter error. This was sent under the group: [Group Name].