I think the issue come with the setting from Joomla! SEF "add a .html suffix to the url", so if you disable this setting from Joomla! configuration panel it should work
Thanks. It worked.
But now there is another problem.
Rss feed is not accepted in feedburner
I checked the flow in feedvalidator.org and he told me " It looks like this is a web page, not a feed. I looked for a feed associated with this page, but couldn't find one. Please enter the address of your feed to validate."