Hello,
Thank you for contacting Rank Math support, and sorry for any inconvenience that might have been caused due to that.
I checked all your sitemap variations in an http status checker and it seems to be returning an error. Please refer to my screenshot below:

Please check this one with your hosting as they might be able to address this.
Looking forward to helping you.
L’hébergeur ne peut pas régler le soucis, je viens de les contacter.
comment faire ?
est ce possible de se donner un rdv pour que vous régler les problèmes sur TeamViewer par exemple ?
bien a vous
Hello,
The sitemap is loading fine now, however, I checked the sitemap URLs with https://httpstatus.io/, and two variations of the sitemap are returning 200 status.
Check the screenshot in the sensitive data section.
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 remove all the sitemaps and submit the sitemap_index.xml in the Search Console.
Hope that helps.
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.