I signed in with this account bud which is a user and I can see them.. I think your mozilla needs fixing. Have you tried closing it and reopening? Or updating it. Look under the help drop down and there should be something in there to help update
Try holding down ctrl when you click that add files button. It sounds like your pop up blocking feature is getting in the way. I had the same problem and was seven shades of pissed before I got it to finally work. I had to make sure that I got it on the first try or else I had to refresh the page.