In Google Search Console, my sitemap isn't detected? Under status, it simply says: 

Couldn't fetch

When I submit it manually, Google Search Console says: 

 Sitemap could not be read

A couple of questions. What URL are you submitting? And also, why is it you are submitting this? (It submits itself)

 

What URL are you submitting?

mydomainname.com/sitemap.php

 

why is it you are submitting this?

Because as I was checking on the indexing of some recent pages from my site, I saw the following error: 

So I went to the Sitemaps tab and noticed that my sitemap wasn't listed there. 

You would need to contact google on this. I can access your sitemap with no problem at all, and the content looks to be fine. So the issue appears to be on their end

I've seen this on one of my Wordpress sites too.

Try to submit the same URL again.

 

Try to submit the same URL again.

Submitting the same URL again worked today. Thanks!