Hello @admindroidturf,
For initial troubleshooting, please make sure that your sitemap is not getting cached. Please follow these steps:
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. If the above steps don’t seem to work, kindly apply the following filter code to your site.
add_filter( 'rank_math/sitemap/enable_caching', '__return_false');
Here’s how you can add filter/hooks to your WordPress site:
https://rankmath.com/kb/wordpress-hooks-actions-filters
Let us know how it goes. Looking forward to helping you.
Thank you.