This usually means you have a confirmation dialog hidden by another window. Look under some of the open applications you have and see if there is a dialog waiting for a click.
Thanks but that's not it. Even if i shut down and restart, i get "another installer is already running."
Try Ctrl-Alt-Delete and see if the installer is listed as a process in Task Manager; you should be able to shut it down from there.
It just occurred to me that you might not be using Windows...
Chatted with Adobe Tech support. I shut down everything labeled Adobe in the Task Manager. That did it. I saved the conversation because i've had this issue before. Thanks for your input.
Following up. This is a summation from Adobe on this issue. This is for Win 8.1.
1.Sign out from CC desktop application and Light room 5
2.End all the Adobe processes.
3.Try updating from CC desktop application. Updated and shows as up to date
4.Click on Light room 5.6 nothing happen.
5.Sign out from CC desktop apps .
6.End the Adobe processes
7.Delete the Light room cookie installer in program data>adobe>Light room folder
I think that last step is just as important,