Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
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 that, remove all your sitemaps from your GSC and resubmit only the primary sitemap (sitemap_index.xml).
After all the above steps, you may give Google some time to recrawl your sitemap and see if this changes the status you see in GSC.
Let us know how that goes. Looking forward to helping you.
I’ve done all the methods you suggested three days ago, but still there is no change in the sitemap.
Hello,
Can you please share your website URL with us so we can further check it on our end?
Looking forward to helping you.
Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
I checked your sitemap page and is loading just fine, however, all of your 4 sitemap URL variations don’t redirect to a final variation as you can see in my screenshot below:

Please follow this guide and redirect to a final variation:
https://rankmath.com/kb/couldnt-fetch-error-google-search-console/#num-5-4-redirect-all-three-other-versions-to-your-preferred-variation
Once done, clear your website cache and try submitting your sitemap to your Google Search Console again. See if this resolves the issue.
We are looking forward to hearing an update from 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.