site map not fetching due general http error

Hello,

Thank you for contacting Rank Math and bringing your concern to our attention. I’m sorry for any inconvenience this issue may have caused you.

Please run your robots.txt using this tool to validate it:
https://technicalseo.com/tools/robots-txt/

Here’s a link for more information:
https://rankmath.com/kb/fix-common-robots-txt-issues/#robots-txt-is-blocking-googlebot

Meanwhile, please follow these steps to flush your sitemap cache:

1. Flush the Sitemap cache by following this video screencast:
https://i.rankmath.com/pipRDp

2. Exclude the Sitemap files of the Rank Math plugin in your caching plugin. The cache could be via a plugin or from the server. For plugins or Cloudflare, please follow this article:
https://rankmath.com/kb/exclude-sitemaps-from-caching/

3. Disable the transient cache for the sitemap by applying this filter. This will make sure that your XML sitemap always reflects the latest changes on your site:

/** 
 * Filter if XML sitemap transient cache is enabled.
 *
 * @param boolean $unsigned Enable cache or not, defaults to true
 */
add_filter( 'rank_math/sitemap/enable_caching', '__return_false');

If you’re not sure how to add this code, you can follow this guide:
https://rankmath.com/kb/wordpress-hooks-actions-filters/

Once done, remove all your submitted sitemaps and resubmit your main sitemap only /sitemap_index.xml:
https://rankmath.com/kb/submit-sitemap-to-google/

Looking forward to helping you.