Hello! I'm sorry you're not seeing your theme applied as you expected. I just tested this workflow and am not able to reproduce the issue you've described.
Could you check the following things and let us know what you find?
- Are there unpublished changes present in your story? If there are, publish the story again and check to see if you still observe the issue.
- Has the theme been unshared? If it has, share the StoryMap theme item with Everyone from your Content page in ArcGIS.
Owen Evans
Lead Product Engineer | StoryMaps