General HTTP error: 404 not found HTTP Error: 404

I installed XML-sitemap and I received this error message in Webmaster Tools. We are not currently blogging.

I received this message:
General HTTP error: 404 not found / HTTP Error: 404

These are my settings:

Result of the last ping, started on March 22, 2016 12:50 pm.
The URL to your sitemap index file is: https://www.xyz.com/sitemap.xml.
Google was successfully notified about changes.
Bing was successfully notified about changes.
Notify Search Engines about your sitemap or your main sitemap and all sub-sitemaps now.
If you encounter any problems with your sitemap you can use the debug function to get more information.

*Basic Options
Update notification: Learn more
Notify Google about updates of your Blog
No registration required, but you can join the Google Webmaster Tools to check crawling statistics.
Notify Bing (formerly MSN Live Search) about updates of your Blog
No registration required, but you can join the Bing Webmaster Tools to check crawling statistics.
Add sitemap URL to the virtual robots.txt file.
The virtual robots.txt generated by WordPress is used. A real robots.txt file must NOT exist in the blog directory!
Advanced options: Learn more
Try to increase the memory limit to:
(e.g. “4M”, “16M”)
Try to increase the execution time limit to:
(in seconds, e.g. “60” or “0” for unlimited)
Try to automatically compress the sitemap if the requesting client supports it.
Disable this option if you get garbled content or encoding errors in your sitemap.
Include a XSLT stylesheet:
(Full or relative URL to your .xsl file) Use default
Override the base URL of the sitemap:

Use this if your blog is in a sub-directory, but you want the sitemap be located in the root. Requires .htaccess modification. Learn more
Include sitemap in HTML format
Allow anonymous statistics (no personal information)

*Sitemap Content
WordPress standard content:
Include homepage
Include posts
Include static pages
Include categories
Include archives
Include author pages
Include tag pages
Custom taxonomies:
Include taxonomy pages for Product Categories
Include taxonomy pages for Product Tags
Include taxonomy pages for Shipping Classes
Include taxonomy pages for Categories
Include taxonomy pages for Tags
Custom post types:
Include custom post type Blocks
Include custom post type Products
Include custom post type Featured Items
Further options:
Include the last modification time.
This is highly recommended and helps the search engines to know when your content has changed. This option affects all sitemap entries.

*Priorities
Homepage
Posts (If auto calculation is disabled)
Minimum post priority (Even if auto calculation is enabled)
Static pages
Categories
Archives
Tag pages
Author pages