Copy the publication link, not the Page homepage
Open the Facebook post and use its share or permalink option to identify the exact publication. Check that the address opens the intended content rather than the Page timeline, profile or a different shared copy. If the post is a video, confirm the service accepts that kind of video-post link. A link to an album or a group does not automatically identify the photo or post inside it. Follow the target format in the current listing instead of replacing it with an easier address.