There could be a few reasons. Maybe the music you want to post isn't licensed for Instagram use, or there might be a technical glitch with your device or the Instagram app itself. Try restarting your device and the app to see if that helps.
It could be that your Instagram account doesn't have the necessary permissions or your app version is outdated. Check for updates and your account settings.
Maybe your internet connection is unstable. Try reconnecting to a better network and see if that works.
Maybe there's a problem with your internet connection. Check if it's stable and working properly.
Maybe it's a technical glitch. Sometimes, the app might have temporary issues that prevent the music feature from working properly.
Maybe there's a technical glitch with the app. Try restarting your device or reinstalling the Instagram app.
Maybe it's a glitch in the app. Sometimes these things happen and it'll sort itself out after a while.
Another possibility is that the music you want to use isn't available in Instagram's music library. Instagram has a limited selection of music that can be used in stories. Try choosing from the available options instead.
It might be that your internet connection is weak, affecting the music playback. Or, it could be that the music you chose isn't compatible with Instagram stories for some reason.
Maybe there's a glitch in the app. Sometimes these things happen and you just have to wait for an update to fix it.
Maybe there's a problem with your app settings. Check if music permissions are enabled.
Maybe there's a glitch in the app or your device settings aren't allowing it.