sitemap_index.xml couldn’t fetch error even after multiple submissions

Hi Team,

I am facing this issue – sitemap_index.xml couldn’t fetch error even after multiple submissions in google search console.

What to do? Facing this with multiple domains. And it’s not feasible to check everyday whether fetched or not? Can you please check? Now I’ve resubmitted so mayn’t be able to see, but again it will show couldn’t fetch. Using RM plugin only.

Please help. Just because of this pages are not indexed and ranking is going down. Thanks.