Maybe this is not an issue, but until today I had not encountered this. On this post, when I click the image to enlarge it, nothing happens. I went to all the other recent posts and had no problem enlarging any image I clicked on. Is that a user’s option to block enlarging their images?
I think what might have happened is the OP didn’t wait for the image to fully load. When you click the final button to post, you have to wait a minute until the little hand thingy appears when you hover over your photo. If you post, then immediately leave that screen, the full-size image won’t load later. If he reposts, it should work.
It’s simply because it’s a very small image (500px), if you post something smaller than 600px it will not open the lightbox.