Hi @OVasileva (WMF)! The hovercard appears blank if an article does not have an intro. It would be great if the hovercard automatically showed text from the first section if this is the case.
Topic on Talk:Page Previews/Flow
Hi @Daylen - thanks for bringing this up. We are addressing this issue, but a bit differently. Since the content of the first section of a page might not present an accurate summary or representation of the page itself, we have put in a special preview type which lets users know that a preview is unavailable - a more-detailed outline of these can be found on the functionality page.