Seeing lots of chatter from photographers struggling to get the newly released Lightroom CC (4/21/2015) to run after it has been installed through the Creative Cloud App. Doesn't seem to matter the platform, Mac or PC, there is a high chance that when you try to launch the program for the first time after updating it will do … well … nothing. It crashes with no sign of anything.
If that is what you are experiencing, you have to use the Creative Cloud App to sign out and then sign back in. Crazy I know, doesn't seem like that should have anything to do with Lightroom crashing when you try to launch it, but Adobe has posted the very instructions on how to do this here.
Bit of a black eye for the launch, but I still think it is easily the best option for photographers to manage and do most post-processing.