It could be that you don't have the necessary permissions or your account is restricted in some way. Also, make sure you're following the correct steps for adding posts.
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.
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.
It could be that you haven't met certain requirements or haven't completed the necessary setup. Check the settings and instructions for adding posts carefully.