I updated the permalink and re-submitted the sitemap to Google Search Console. Unfortunately the problem still exists.
My host is ‘one.com’ and I am using Safari browser on a Macbook pro.
First: I can confirm that I submitted the correct sitemap (https://www.marifoonbewijs.nl/sitemap_index.xml).
Second: I am using DIVI theme which might be causing the issue. However, their customer service recommended me to contact Yoast.
I tried to add the code below to my htaccess but it did NOT work:
# WordPress SEO – XML Sitemap Rewrite Fix
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^sitemap_index\.xml$ /index.php?sitemap=1 [L]
RewriteRule ^([^/]+?)-sitemap([0-9]+)?\.xml$ /index.php?sitemap=$1&sitemap_n=$2 [L]
</IfModule>
# END WordPress SEO – XML Sitemap Rewrite Fix
