if you want to include one HTML file into another using “#include” then file extension should be changed to “shtml” otherwise it will not work properly…
Do you have your include code in an html page or an shtml page or a php page?
for the html (shtml) I use this: <!–#include file=“filename.html”–> wherever I want to include the file.
If you have it in an html page, first try renaming your index page to index.shtml to see if that works. If it does, you can leave it as that name. If you want it to continue as .html, you need to make sure that your htaccess file has your html parsed as shtml.