Hello,
Thank you for contacting us and sorry for any inconvenience that might have been caused due to that.
Can you please try to follow the steps below and see if that works for you?
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/hook to your WordPress site:
https://rankmath.com/kb/wordpress-hooks-actions-filters/
If your categories are empty then you can enable the option Include Empty Terms from WordPress Dashboard > Rank Math > Sitemap Settings > Taxonomies: Categories.
For the author sitemap, please enable the Author Archives from Rank Math > Titles & Meta > Authors and make sure that the Author Robots Meta is set to index.

Once done, you will be able to find the Author option on your Sitemap Settings.
Let us know how it goes. Looking forward to helping you.
Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.