If you have a user with custom role (read this post about roles and capabilities), you will not able to assign it as author to a post. This is due to a WordPress bug. For now, there’s a workaround: add level_1 capability to your custom role. Method 1 add_role(‘custom_role’, ‘Custom Role’, array( ‘level_1’ => true … … Continue reading Assigning user with custom role as author to posts in WordPress