It could be due to restrictions on your account. If Instagram has detected some unusual activity on your account, it might limit sharing features. Also, check if your friends have any restrictions on their accounts that prevent them from reposting. For example, if their account has been flagged for some minor violations, they may not be able to perform actions like reposting.
First, check your story privacy settings. Make sure it's set to allow sharing. If it's set to private or only viewable by a specific group, your friends won't be able to repost. Just change it to public or a wider sharing option if you want them to be able to repost.
Well, there could be several reasons. Maybe your story is set to private and not visible for reposting. Or perhaps your friends' accounts have some restrictions. It's also possible that they just haven't figured out the reposting feature yet.
Maybe they don't have the option enabled or there could be some technical glitch. Check if your settings allow reposting and if their accounts are functioning properly.