Won't open on my Mac either. Photoshop CC is ok.
I have tried uninstalled both the new lightroom and the old lightroom, reinstall the new lightroom, reboot. Still will not run.
Now, where can I get the stand alone version of Lightroom again to get up and running?
Awesome update Adobe!
i just saw a suggestion that worked for me in another thread - sign out from adobe CC - go under "preferences", sign out (not just quit) and then sign back in. then it works! good luck!
This solution worked for me too.