RSS has stopped working

I have put up a number of web sites for friends using WordPress, sometimes just for simple blogging and sometimes as a complete web site. On one of those web sites RSS nolonger seems to work. Can anyone please help?

The site is at: https://messenger.thoughtfactory.biz

Note: I upgraded the site to the latest version, but that didn’t help.
I also looked at the posts of people who had similar problems, bbut none of their solutions seemed to apply.

If I go to – https://messenger.thoughtfactory.biz/wp-rss2.php?feed=rss2
(as suggested elsewhere)

Fatal error: Call to undefined function: get_settings() in /hsphere/local/home/tobeyjag/messenger.thoughtfactory.biz/wp-rss2.php on line 10

which is –
header(‘Content-type: text/xml; charset=’ . get_settings(‘blog_charset’), true);