MacBook – Unable to join Photo Stream on OS X 10.8.5

I received an email invitation to join a Photo Stream. When I clicked on the "Join this Photo Stream" link on my MacBook Pro, I was taken to a page with the following message:

Photo Stream

Follow these steps to join a shared photo stream

1. Make sure you have an iPhone, iPad or iPod touch running iOS 6 or a Mac running OS X 10.8.2 with iPhoto 9.4 or Aperture 3.4 or later
   installed.
2. Sign in to iCloud on your devices.
3. Open the invitation email on an updated device and tap the Join this Photo Stream button.

I was running OS X 10.8 at the time, so I upgraded my OS, and I now have 10.8.5. However, when I click on the link to join, I still am taken to the same page. There doesn't seem to be a caching issue, because I cleared my cache and also opened the link in a different browser.

I'm logged in to iCloud, and I'm able to create a Shared Photo Stream through iPhoto (v. 9.4.3) and share it with others, and they can see the photos in the stream. However, I don't see the Photo Stream that was shared with me, and I still get the above message when I click on "Join this Photo Stream" in the original email.

I already tried copy/pasting the link from the email to the browser, and I still get the same page and message. I've also restarted my machine, logged out of iCloud and back in, quit iPhoto and restarted it, and pasted the link into both Chrome and Safari after clearing the cache.

Is it possible that I need to have OS X 10.8.2 instead of 10.8.5 in order to accept the invitation to the Photo Stream?