Categories not displaying in Post Admin

Since the latest wp update, for some reason when adding or editing a post there is no Categories section on the right. I mean the whole side-sortable postbox-container #categorydiv.postbox does not display. I can see in the Inspect Element that is set to display:none however the css is core file related:

.hidden, .js .closed .inside, .js .hide-if-js, .js .wp-core-ui .hide-if-js, .js.wp-core-ui .hide-if-js, .no-js .hide-if-no-js, .no-js .wp-core-ui .hide-if-no-js, .no-js.wp-core-ui .hide-if-no-js {
display: none;
}

I tried writing css in my theme style.css to make it display but that did not work. I didn’t think it would but it was worth a shot.

After searching for this issue in the forums I did the following: I did a complete backup, I deactivated all plugins to see if the problem resolved but it did not, I looked in the header.php for the list_categories line of code but it is not in my header.php file, I saved a copy of my wp-content and wp-config.php and re-installed wp however keeping my original wp-content and wp-config.php and it did not resolve.

The categories choices are displaying in Page edits and additions. Just not Posts. They are also present under admin menu choices Posts > Categories. It’s just on the Post edit and new that they do not display.

By the way, the Tags sortable postbox is not available either in Posts but is on Pages.

Right now we can set the categories via quick edit but we need to have them display on the post admin pages as well. Any ideas?

[ No bumping please. ]