Starting with the release of Strategy ONE (March 2024), dossiers are also known as dashboards.
This article describes a situation where some of the cover images for Dossiers cannot be seen in the Workstation.
When users are browsing through the Dossiers using Workstation, they may see that for some of them, cover image is not available with the error message “Cover page not found”:

This may happen for the images coming from external sources, like Sharepoint.
Workstation doesn’t support displaying cover images that require authorized access. It doesn't share the context with the system browser, hence don't pass any tokens when sending requests for cover images.
This is working as expected. One of the workarounds would be to provide accessible URL to the image, that doesn’t require any additional authorization.