There could be several reasons. Maybe your internet connection is unstable, or the image size or format is incompatible. Also, make sure you're following the correct steps for adding pictures as per the platform's instructions.
Maybe there's a technical glitch or a limit set by the platform you're using. Check if there are any error messages or guidelines for adding multiple pictures.
It could be that your story format or the app you're using doesn't support adding a second picture. Sometimes, it might be a matter of subscription level or specific settings that need to be adjusted.