Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
Can you 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. After doing so, remove all your sitemaps from your GSC and resubmit only the primary sitemap (sitemap_index.xml).
Let us know how that goes. Looking forward to helping you.
I have done the first step whikch s flushing it didnt work, the second step which is exclude sitemaps from caching. The steps on the site are not there, theres no performance button
I have removed the old sitemaps on Google Search Console
Hello,
Can you please share your website URL with us so we can further check it on our end?
Looking forward to helping you on this one.
Hello,
I noticed that your sitemap is generated by a different plugin/service as you can see in my screenshot below:

Please ensure to deactivate that sitemap generator from your website’s backend. If the sitemap is added as a physical file. You may open your FTP and locate the XML file in the root directory of your website.
After doing so, repeat the steps I presented earlier and see if the issue finally goes away.
Looking forward to helping you on this one.
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.