The Smugmug Gallery share does not work for me.
When it gets to step 3/3, there is no ability to add photos (I had previously selected the ones I wanted to upload), and nothing is sent to Smugmug.
I'm having the exact same problem. I get to screen 3/3 then get an empty dialog box.
I emailed SmugMug support - they are apparently aware of the issue and are working to resolve it. No ETA, however. They didn't seem to know whether it was an adobe issue or smugmug issue though. Apparently it's a "new issue that just came up". Weird. Hopefully they can fix it.