It could be that the story has reached its post limit or there's a problem with the platform's functionality. Try refreshing the page or contacting the support team for help.
There could be several reasons. Maybe the post format isn't supported by the story feature. For example, some platforms only allow certain types of media like photos or short videos. Another possibility is that there are privacy settings preventing you from adding it. Check if your account settings limit the sharing of this particular post to your story.
One possible reason could be a technical glitch in the app. Try restarting the app or your device. Another reason might be that the post format isn't compatible with the story. For example, if the post has a file type that the story doesn't support.
It could be that you haven't completed certain settings or don't have the necessary permissions. Check your account settings and make sure everything is configured correctly. Also, see if there are any specific requirements for adding posts to the story that you haven't met.