The issue is that if you do a lot of pictures, and if they are a little big, it can take a while for the uploader to finish, and it doesn't give you any sort of 'status' on the upload.
It's kind of clunky and requires patience and trust
I thought the same thing and would hit the upload button again. Then I noticed at the very bottom left of my screen, a very faint (gray color) and small loading %. You really have to look to see it. I use Chrome and the "blue skin" (not Woody). One thing I should mention is that the upload button, is really not a button, but just the words. That also took me awhile to figure out.