To use the regular Joomla SEF, it is required to use a .htaccess in the root of each website.
So if you don't have a htaccess, add it or share the one present in your master.

This is the ".htaccess" that redirect all the pages to the "index.php" and allow joomla converting the SEF url into internal URL.
So without htaccess, all the pages returned 404 and the htaccess does not redirect to the "index.php"

I'm having the same problem, see my post

www.jms2win.com/en/forum/24-joomla-multi...site-to-use-sef-urls

I've tested switching on the SEF URL settings in the global config settings and copied the .htaccess file into the route of the slave site and still get taken to a 404 page. The url appears to norw resolve correctly it simply cannot find the page.

Is this because SEF URL's need to be switched on at the master site also?
I realise each site will have its own .htaccess file but is this affected in someway by the dynamic linking of the slave sites?

regards Nick

No you don't need to enable the SEF in the master.

The SEF must only enabled in the slave site configuration.
Something that you may have to check is the ".htaccess" and the "rewritebase" field that may perhaps solve your issue.
When it does not have a correct value, sometimes, this may result with an error 404.
So verify you SEF configuration.

This current www.jms2win.com website is a slave site that enable the SEF and you can see that the URL are correct.