This URL is the image proxy, not a gallery. The root path / has no product image by design.
https://cdn.plectar.com/cdn-health → plain text OKhttps://cdn.plectar.com/productimages/…/file.jpg (full path after your Worker host, same as on cdn.plectar.com)https://cdn.plectar.com/12345_filename.jpg (filename only at path root)If the Worker runs on the same hostname as PLECTAR_CDN_ORIGIN (e.g. cdn.plectar.com), set PLECTAR_CDN_RAW_ORIGIN in Worker variables to the origin that serves raw /productimages/ files.
In Odoo: PIM Settings → Images CDN → use diagnostic buttons; grep server logs for pim_plectar.cdn_diag.