WordPress tries to create a custom post type when Elementor loads. The system already holds a post type with the same slug. WordPress stops the second registration and Elementor writes an error to the log.
The conflict usually comes from another plugin, a theme function, or a migration that left old entries in the database. When the slug matches Elementor’s internal types such as elementor_library, Elementor cannot add its wrapper.
Because the post type is blocked, Elementor does not list the type in Theme Builder conditions or template dialogs. The editor may show a generic failure message.
Debug logs reveal a line that mentions “post type already exists”. The global $wp_post_types array contains the duplicate entry.