Facebook is currently incorrectly flagging some sharing URL as not having setup the correct level of access for the facebook scraping tool that pulls in the image and link description for posting.
At the moment, the Studeo team has confirmed we have the correct level of access setup on the robots.txt file to allow facebook to easily scrape each Storybook for the content it uses for a post.
The issue does resolve within 24 hours of the initial posting problem, but generally within 4-6 hours it is ready to go. You can always check the state of your Storybook link here: https://developers.facebook.com/tools/debug and when ready can post.
Interim Solution
When posting, you can first run your Storybook URL through the above Facebook Sharing debugger to check if it is ready to post, doing so will also trigger Facebook's own system to resolve the issue.
If you choose to post ahead of the resolution, you can repost later to get the image in place, OR you can use the GIF or Static Sharing Image Studeo creates and places in the Share and Embed Menu for each Storybook.
Studeo's Incoming Solution
Studeo is working on 2 different solutions, one to come out in early Q2, and the other later on this year. Both of them require no change of behaviour or information needed to post to facebook, but will ideally work around both issues at the moment with Facebook and any future issues that may arise.