Sitemap index.xml or Sitemap.xml?

[Pooja]

my website let's say.... www.example.com is a WordPress website that has a sitemap like www.example.com/sitemap_index.xml generated from Yoast.
But now when I type www.example.com/sitemap.xml it does not redirect to www.example.com/sitemap_index.xml as it supposed to be... as I learned Yoast provides redirection on its own.
But there is an error... I have submitted sitemap_index.xml to Google search console it works well.
Should I worry about sitemap.xml as this displays an error every time I try it? What to do? How to resolve the issue? Please help!

[edited by: engine at 9:23 am (utc) on Mar 24, 2021]
[edit reason] Please use example.com [/edit]

[not2easy]

On a WP site, the www or non www is determined within your settings. IF Google is happy with a version of the sitemap that you cannot view, I would say that is unusual but indicates that you have submitted the correct version to Google. Look at the settings within Admin > Settings> General Settings and the URL displayed there is the URL you should be using.

Yoast can only redirect to the URL entered in "Site Address" because all the pages have that address as their correct URL.