I configured sling sitemap generator in my SP13 environment and it only works with the "On demand" option. I've used this blog as a reference to my configuration: https://www.theaemmaven.com/post/aem-apache-sling-sitemap and everything looks correct.
I was using SP8 and had to upgrade to SP11 to work in this feature and everything works fine with SP11. Once I've upgrade to SP13 (which is the one the client is using) the sitemap is not generated in /var/sitemaps. I can see in sling scheduler status that my scheduler is there, and also increasing the log level to trace I can see that it's running, but there's no indication as to why it's not saving the sitemap.
Any ideias on why this may be happening?
If you created a brand new instance and deployed a new archetype project, you may see an empty sitemap. You need to publish /content/mysite/us/en first. When running on the author, the sitemap generator will only consider published pages. Try publishing the pages and see if it's generating the sitemap or not.
Hope this helps.
Please verify if you have proper service user configuration, as document say it needs org.apache.sling.sitemap:sitemap-writer process ACLs for /var and proper read access as well.
Refer below readme file for more information
Hope this helps !!!