This error indicates that the HTTP server has returned an HTTP/403 Forbidden error.
Things to try:
Check that you are attempting to access the correct
URI.
Check that you are able to access the
URI from a web browser.
If the
URI requires authentication, then check that you are supplying any required authentication credentials (e.g. via the
username
and
password
settings).
NOTES: iPXE together with Apache2 reports this error if the file is a symbolic link, and the target of the link does not exist.