One way is to rename the file extension to .xml.
If you can’t do that, copy the code, delete the file and create a new one with the same name (or different if you want) but with .xml instead of .html. Then, paste the code back in.
The problem is it isn’t in .html but .xml, It looks like that Google is unable to pass security system of infinityfree. (It is actually supposed to be accessible by google?)
@CarlosSantos Can you use cloudflare for your website? because it disables the security system so google crawler should be able to access your site.
Try opening devtools and navigating to that webpage on your browser. In the network requests, it should have the ability to show the content type of your page. If it’s text/html, then it will be your configuration itself.
Otherwise, it truly is infinityfree returning an error page (or something else having to do with inaccessibility).
IMPORTANT: Make sure that the line RewriteEngine On is not repeated twice. In case the line already exists, simply copy the rest of the code without it.
Is that Wordpress you have up or ??
I think you can simplify everything and open an account on cloudflare