Look at the app settings. There might be a permission or setting that is turned off and preventing the sharing. For example, check if the 'Share to My Story' option is enabled in the app's privacy or sharing settings. Also, ensure that your account is in good standing and not restricted in any way.
Perhaps there are some restrictions based on the content of the story or your account status. It's worth reaching out to the app's support team to figure out exactly what's going on.
Perhaps there's a technical issue preventing them from sharing. Or they might have concerns about sharing it for some reason that they haven't told you.
There could be a few reasons. Maybe your story is set to private, or your friends' social media platforms have some restrictions. Another possibility is that they just haven't figured out the sharing function.