me too. one i made earlier today was working within a post; then i changed the photos but not the tags, and suddenly it didn't work.
so i re-did everything with new tags and a new post. still no dice.
i've just made a completely different post, referencing different photos on my flickr account, all tagged correctly... and yep, it's not showing up in my post at all.
meanwhile, an old post containing the exact same [slickr-flickr tag="----"] format is working just fine. argh!
site is http://www.magdalen.com ~ the newest one that does not work properly is called "Manifest Destiny --- 10 May 2013 --- Bones." it should point to/include photos from: [slickr-flickr tag="05-09-2013-manifest"] but does not work. the URL is http://magdalen.com/manifest-destiny-10-may-2013-bones/ .
another one that's not working: http://magdalen.com/manifest-destiny-13-may-2013/ (this one does show a single photo --- that is because i uploaded it manually as a "set featured image". it has nothing to do with slickr flickr).
yet http://magdalen.com/who-owns-what/ works just fine.