Not sure why it’s not displaying on that page but it’s fine here: https://www.beboparket.nl/sitemap/
So I think it’s probably an issue with that specific subdomain rather than the plugin.
The error will not occur due to a subdomain. see a fatal error below
Fatal error: Allowed memory size of 277872640 bytes exhausted (tried to allocate 16777224 bytes) in nieuw.beboparket.nl/wp-includes/wp-db.php on line 2727
If i use: [simple-sitemap types=”product”] it works but pages not
Do you have a lot of products to display by any chance?
I suspect this is more of an issue with your WordPress PHP memory limit size than with the plugin itself. The memory limit can be reached for many different reasons.
Here are some links to more information about this and some solutions.
