Portfolio items Permalinks slug 404

Hi,
I’m still having an issue with one of our site; http://www.gocaravan.com
All our pages seem to be falling on a 404, we’d like to use the custom permalinks so we have /vehicules/carname as url.
I’ve read about the rewrite flush plugin, installed it, flushed everything, deleted my cookies. But this didn’t seem to fix the issue.

If you could support us with this it would be appreciated.

Thank you