This error indicates that the web server returned an HTTP status code of 404 (Not Found).

Note that the same error can occur if the automatic TLS certificate validator does not find a cross-signing certificate on http://ca.ipxe.org/ for the TLS certificate of the server you're trying to connect to.

Things to try:

• Check the URL that you are attempting to boot from.

• Try downloading the URL using a web browser, or command-line client such as wget.

• Check your certificate trust settings.