Bug Sitemap.xml

Hello,

my Sitemap.xml link doesn’t work: https://growbility.de/sitemap_index.xml. When I open the link https://growbility.de/?sitemap=1 I can see the URL to https://growbility.de/page-sitemap.xml, but it a click on it also deliver a 404er error. In the Yoast Settings the sitemap.xml is enabled.

The page I need help with: [log in to see the link]