Are you using the Frontend Submission extension? In that extension, we hide all default post fields in the admin area, to make them not duplicated with the default WP UI.
Yes, we are using the Frontend Submission extension. I'd like the fields to show up both on the frontend and in admin (replacing the default WP UI fields). The reason is that we are trying to customize how data is input in the admin with metabox fields instead of default WP fields.
I've just updated the plugin to show the fields in the admin if the post type doesn't have support for them. If you want to show them, make sure you remove post type support for the post type, like this:
add_action( 'init', function() {
// Remove post type supports and show Meta Box fields for them.
remove_post_type_support( 'post', 'title' );
remove_post_type_support( 'post', 'thumbnail' );
} );