LagunaLife Right. If you deleted the sitemap.xml file, then it must have been there to start with, so that could explain it. Can you disable the extension, check to ensure no sitemap.xml file exists in the root of flarum, then re-enable ?
Test by loading the sitemap.xml file directly in a browser, and see if this reflects the true posts in your forum.
To be clear, sitemap.xml is dynamically generated, and should never be created by hand as per https://discuss.flarum.org/d/14941-flagrow-sitemap/80