Hi,
Hope this will help someone:
I have WordPress in a subfolder.
In the site root I have static shtml pages, on which I run the RSS2HTML script -> https://www.feedforall.com/download.htm – to extract CATEGORY RSS feeds from my WP install to the static shtml pages with Server Side Includes (SSI).
So I have in any given shtml page a <!--#INCLUDE VIRTUAL="rss2html.php?TEMPLATE=my-template.html&XMLFILE=https://www.mysite.com/wpfolder/category/category-name/feed/&MAXITEMS=5" -->
tag.
I scratched my head until I found this thread, because while setting this up and testing, the category RSS feeds displayed the entire feed, all categories included.
So, now I have disabled Simple Tags, and FINALLY, my category feeds come up by category.
I then enabled Simple Tags again, and unchecked ( Active tags for page ) as kadiko suggested.
All fine now. Cheers.