OG Tags allows your content render a rich preview on shared on social media or chat apps such as WhatsApp. However - these previews are not always consistent in format and previewing a vertical story makes it even more problematic to set up.
Follow these steps to set up correct previews for your story:
1. Go to Story Mode (top right):
2. Click the Additional Configs in the left side menu
3. Set up (individual) preview images for Facebook, Twitter, LinkedIn and WhatsApp.
Please note that the aspect ratios for the previews are defined by each respective network - so you will have to compromise for a 16:9 or square image that illustrates your vertical story.