This morning we discovered that the SEF structure of tags in Joomla 3.6.4 produces an item like this URL: ../component/tags/tag/4-tag.html. After searching around for a solution, the best we could do with out spending days debugging, was to set up a menu item pointing to tags, then set a .htaccess rewrite. For example: RedirectMatch 301 ^/component/tags/tag/(.*)$ /blog/tags/$1 . That this little trick does for those who do not know, is it sells the server if a request is made for any URL with this element "/component/tags/tag" to be redirected/rewritten as "/blog/tags/(var)". So, the item becomes /blog/tags/4-tag.html. This has solved the problem for the time being.