WP_Error: Invalid HTTP response code

WordPress uses the HTTP API to request external resources. When the API receives a status code outside the 200‑299 range it returns a WP_Error with the message Invalid HTTP response code. The error appears because the remote server responded with an error status, a network problem prevented a successful request, or the local environment failed to negotiate a secure connection.

The error stops plugin or theme installations, blocks API calls, and prevents remote data from loading. It signals that WordPress is unable to verify the response as successful.