Hello,
I tested the URL with https://httpstatus.io/ and in the sitemap, the URL is added without the WWW variation but upon accessing, it redirects to the WWW variation and then returns a 404 error.
Here’s a screenshot for a quick reference:
https://i.rankmath.com/BjuFUa
I then checked all the variations of your website and two variations are returning 200 status and one variation has a double 301 redirection.
Except for the preferred variation (which should return only a 200 status), all the non-preferred variations of the website should redirect to the preferred variation and return a 301 + 200 status.
Please follow the steps in this link:
https://rankmath.com/kb/couldnt-fetch-error-google-search-console/#5-check-for-the-correct-version-of-the-sitemap and redirect to the correct variation.
You can also get in touch with your web host regarding this.
Once this is fixed, please flush the sitemap’s cache again by following the screencast shared by my colleague and see if that fixes the issue.
If the issue persists, we might need to take a closer look at the settings. Please edit the first post on this ticket and include your WordPress & FTP logins in the designated Sensitive Data section.
Please do take a complete backup of your website before sharing the information with us.
It is completely secure and only our support staff has access to that section. If you want, you can use the below plugin to generate a temporary login URL to your website and share that with us instead:
https://wordpress.org/plugins/temporary-login-without-password/
You can use the above plugin in conjunction with the WP Security Audit Log to monitor what changes our staff might make on your website (if any):
https://wordpress.org/plugins/wp-security-audit-log/
We really look forward to helping you.