Thread:Extension talk:RSS/Failed to load RSS feed from https server. Error fetching URL: Peer certificate cannot be authenticated with known CA certificates/reply (4)

The message

Error parsing XML for RSS

comes from older RSS extension versions. Apart from a possible SSL problem, you need to use the version indicated on the RSS article page:

2.15 r114168 (2012-03-19 (use revision r114168 in SVN))

Warning: the version in git is currently not up to date (due to pending code reviews).

Older versions did not correctly parse all kinds of feeds. A good way to check the extension is to copy the XML feeds from the original server to a different non-SSL server and then to let the RSS extension load from there.