First, check the post content. If it contains something that violates the platform's rules, like offensive language or copyrighted material, remove or modify it.
There could be several reasons. Maybe the post format is not compatible with the story feature. For example, if it's a very long video and the story has a limit on video length. Another possibility is that there are some restrictions on your account, like if your account is new and still in a verification process, or if you have violated some community guidelines in the past which has led to a temporary or permanent restriction on adding posts to stories.
It's relatively common. Instagram is a complex platform with various features and settings. So, things can go wrong easily. For example, if there's a sudden update to the app, it might disrupt the normal functionality of adding posts to stories until the user adapts to the changes or the app developers fix any emerging bugs.
Ensure your privacy settings are correct. If they're too restrictive, adjust them. If it's a technical issue, wait for a while and try again. The platform might be having temporary glitches. You can also try logging out and logging back in.
It could be that the platform has certain restrictions or requirements that haven't been met. For example, the content might not comply with the platform's guidelines or the person trying to add it doesn't have the necessary permissions.
It could be that you haven't met the requirements for adding a post. For example, maybe you need to have a certain number of followers or complete some settings first. Check the app's help section for specific criteria.
It could be that you haven't met certain requirements or conditions for adding posts. Check if there are any specific rules or settings you need to follow.