One client recently had a problem using the Yoast SEO plugin returning an error, file not found.
Investigating via google we found the answer directly via the Yoast.com website. You’ll need to update the htaccess file and add the following code before the bulk of standard WordPress entries. Any of our clients who require assistance with this can drop us a line.
# Yoast SEO - XML Sitemap Rewrite Fix RewriteEngine On RewriteBase / RewriteRule ^sitemap_index.xml$ /index.php?sitemap=1 [L] RewriteRule ^locations.kml$ /index.php?sitemap=wpseo_local_kml [L] RewriteRule ^geo_sitemap.xml$ /index.php?sitemap=geo [L] RewriteRule ^([^/]+?)-sitemap([0-9]+)?.xml$ /index.php?sitemap=$1&sitemap_n=$2 [L] RewriteRule ^([a-z]+)?-?sitemap.xsl$ /index.php?xsl=$1 [L] # END Yoast SEO - XML Sitemap Rewrite Fix