This error is usually caused by an error when pulling content from external URLs.
Facebook either doesn't recognise the content in the link or can't connect to the link.
Common Error Messages Shown for this Issue
The URL you supplied is invalid — Invalid URL — Failed to parse URL
Unable to fetch video file from URL — Unable to fetch video file from URL — Unable to fetch video file from URL
Service temporarily unavailable — Can't Download — Could not retrieve data from URL
Empty reply from server
Please check your link url to make sure it's correct. Then try again.
The link may be correct but the site where it lives may be down. Check the actual site to make sure.