So I'm having some issues with this and I can't see why. I just need a custom role that can access the blog in the back end.

I've added a new post type with a Capability type of blog and a new user role with all the caps fr it that would allow admin access users to add/edit the custom post type. This works for admins and they can access the post type in the back end. However users of my custom role can not get into the back end at all.

Post type args of note

"capability_type" => 'blog',
"map_meta_cap" => true,

Register role

function add_blog_manager_role(){
    add_role(
        'blog_manager',
        'Blog Manager',
        array(
            'read' => true,
            'edit_posts' => false,
            'delete_posts' => false,
            'publish_posts' => false,
            'upload_files' => true
        )
    );
}
add_action( 'admin_init', 'add_blog_manager_role', 4 );

Add Caps

function add_blog_role_caps() {
    $roles = array('blog_manager', 'editor','administrator');
    foreach($roles as $the_role) {
        $role = get_role($the_role);
        $role->add_cap( 'read' );
        $role->add_cap( 'read_blog');
        $role->add_cap( 'read_private_blog' );
        $role->add_cap( 'edit_blog' );
        $role->add_cap( 'edit_others_blog' );
        $role->add_cap( 'edit_published_blog' );
        $role->add_cap( 'publish_blog' );
        $role->add_cap( 'delete_others_blog' );
        $role->add_cap( 'delete_private_blog' );
        $role->add_cap( 'delete_published_blog' );
    }
}
add_action('admin_init', 'add_blog_role_caps', 5 );

I've been googeling frantically trying to find the cause of this. I've tried with plural, non plural caps, tried adding capabilities into the post type args. However I'm never able to get into the back end. I've not got any other code in the theme that might kick users out of the admin (I removed my own code that kicked them out while testing this)