Photos won't upload to iCloud

I recently upgraded from iPhoto to Photos (Version 1.0.1 (215.65.0). I also purchased more space on iCloud to hold all of my photos. I've set up everything as directed to sync my photos to iCloud. None of my old photos will sync to iCloud from Photos library. It seems to hang on updating forever with no progress. It does sync "down" photos that I take on my iPhone from the iCloud. For instance, photos I take on my iPhone show up in the Photos app on my computer pretty quickly. When I go to iCloud.com and look at my photos there it has photos I've taken on my iPhone but none of the older photos from my library. I've tried to upload for days at a time and nothing goes. What do you think? I'm about ready to give up on iCloud and go back to Dropbox.

Things I have already tried: rebuilding the Photos library, restarting computer, signing in and out of iCloud, stopping and restarting sharing on all my Apple devices.