Have installed/uninstalled Lightroom CC several times. Followed the instructions that I read on this board. Here is what I did the last two times.
1) uninstalled LR . 2) Signed out of CC Desktop App (not just 'quit') 3) Rebooted MacBook Pro. 4) Signed in. 5)Downloaded LRCC. 6) Attempted launch. 7) Didn't work.