Problems with export the posts in a .xml file

I tryed from “wp-admin/export.php” to download the posts and the rest of stuff, as i was used to until now with wordpress, being possible that.

After I downloaded the file, I observed that it has 2 Kb and inside the file, in the code, there were no articles, but was a HTML copy of the wp-login.php. file, that is what I found reading the file code .xml. I have changed the ending in .html and I loaded the page, then I recognized the elements of the wp-login.php. page.

Please, if you have any idea about the issue, I would like to know.

Thank you!