in my sitemap not showing all posts

Hello, we apologize for the issue you are facing with your sitemap not showing all your posts. There are a few reasons why this might happen:

1. Custom Canonicals: If you have added custom canonical URLs to your posts, those posts may not appear in the sitemap. Rank Math includes a self-referencing canonical for all posts set to Index by default. To ensure all your posts are included, consider removing any custom canonicals from them.

2. Sitemap Settings: Check your sitemap settings in Rank Math to ensure that there are no exclusions set for your posts. You can find these settings under Rank Math SEO → Sitemap Settings.

3. Plugin Conflicts: Sometimes, other plugins can conflict with Rank Math and affect the sitemap generation. You can check for conflicts using the Health Check plugin.

4. Server Resources: If your server is under-resourced, it might struggle to generate a complete sitemap. You can check your server’s PHP settings by navigating to Tools → Site Health → Info in your WordPress dashboard and ensuring that the values meet the recommended requirements.

If you’ve checked these points and are still having issues, please reply to this ticket, and a human agent from the Rank Math Support team will assist you further.

Thank you for raising this concern!

Sources:
Rank Math Sitemap Issues and Their Fixes » Rank Math

Hello,

Thanks for contacting us, and sorry for any inconvenience this might have caused you.

One possible reason can be that your sitemap is heavily cached. Please follow the steps below to see if it 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 doesn’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/

Once done, remove all your submitted sitemaps and resubmit your main sitemap only.

Let us know how this goes.