I have the same issue. It's been commonly reported for a considerable period of time. So not new.
I have not found a solution. At least not one that worked.
It seems that when the site is installed in a subfolder and then the URI is set to the root (or simply a different "folder") two things break.
1) The admin bar vanishes.
2) The site does not "think" you are logged in, which means things like "edit post" links don't show up.
My guess is that it's a cookies issue causing both problems. Which suggests to me it's a bug or feature deficiency in the way WP handles admin cookies.
I'd love to find a working solution.
One solution folk reported working was to add
@define(‘ADMIN_COOKIE_PATH’, ‘/’); into the config.php file. However, on my site this made no difference.
Let me know if it makes a difference for you.