The error appears when Elementor attempts to load the template library and the JSON payload is malformed. Elementor validates the payload before it displays templates. If validation fails the editor shows a toast with the message.
Typical triggers include a database option that stores the library data, insufficient PHP memory, file‑system permission restrictions, a timed‑out HTTP request to Elementor’s CDN, an outdated plugin version, a conflict with another plugin or theme, a PHP version below 7.4, or MySQL strict mode which truncates long strings. Each of these conditions can corrupt the JSON or prevent it from being retrieved.
When the payload is rejected the library panel remains empty, import actions stop, and the page editor may refuse to load additional sections. Users experience a broken workflow and must resolve the underlying condition before templates become available.