First, check the app settings. Make sure sharing to story is enabled for your own posts. If not, toggle the relevant option on. It could be as simple as that.
One possible reason is that the post itself has some issues. For instance, if it contains inappropriate or copyrighted material, the platform may not allow you to share it to your story. Another aspect to consider is the format of the post. Some platforms only support certain types of posts (like photos or videos) to be shared to the story, so if your post is in an unsupported format, that could be the problem.
Yes, there might be. Check if you have the correct permissions for sharing on the app. If not, enable them. Also, restart your device. Sometimes, a simple restart can solve glitches that prevent sharing.
It could be that your account settings are restricting the sharing feature. Check your privacy and sharing settings to make sure everything is enabled correctly.
It could be that your account settings are preventing the sharing. Check your privacy and sharing settings to make sure they allow sharing to your story. Also, make sure the post you want to share is allowed for such sharing.