This is happening to me as well, although, my problem didn’t start occurring until I changed who the author of the post was.
I made the site for a client, and created their first few articles. During this time, the site properly showed the author as “admin”. But once I switched the article over to a different user it no longer shows.
All of the users info is filled out for their profile, and everything looks ok with entry_meta in functions.php of my theme.
Does anyone have any thoughts?
