I had the same problem earlier today. Sign out of your account for CC in the Preferences panel, close the CC toolbar app. Then sign back in, and the download process might begin in earnest for you. Took me SIX HOURS to download this pig, and now it crashes continually. This software is not ready for release based on today's experience. Hopefully you will at least be able to get to the level of frustration I have arrived at, beyond the level of frustration you are currently stuck at trying to get it to work.I am on the same OS. Too bad Apple abandoned a pro level competitor to LR. Hopefully in the near future they will update Photos so that it competes well with LR.