Created xml sitemap points to 404 page

Dear support,

I’m aware that my question is not part of standard support but more general question.

I’m using WordPress SEO by Yoast plugin on my sites, and I used it on Enfold to create XML sitemap and the result points to the 404 page.
When I did the search on the Yoast support about this topic, I found this: http://kb.yoast.com/article/77-my-sitemap-index-is-giving-a-404-error-what-should-i-do so, Yoast explains that “First of all, let us be clear that this is not due to our plugin, but due to poorly coded themes and/or other plugins.”

Ok, I suppose that your awesome theme is well-coded but is there any advice that you can give me what could cause this and how can I improve it within your theme? Thank you, guys!
Alfiya