You didn't need to uninstall the CC version. LR 6 and CC is the Exact same program, same download and same file get installed on your hard drive. The difference comes from how you sign in.
As to your current problem is sounds like you have some type of computer problem.
If there's a computer problem, it's something that is escaping me. I've been using Macs since 1986 and I'm pretty good at trouble shooting. I didn't have lightroom CC. I had an older trial version of CC with photoshop. I bought the creative suite (minus lightroom) at an education discount but stayed with Aperture until it was no longer supported. I have been using the native Mac photo program, but I really needed something better so I bought the stand alone Lightroom 6. After cleaning up the older CS programs, un-installing the old trial CC (without Lightroom), running some diagnostics, etc. I find it hard to believe that I'm the only one that has ever had this problem of the blank installation window. Thanks for your comment.
Were you able to resolve this issue? If not, perhaps posting a screenshot of what you're seeing and your System Information would help users and staff narrow down the cause.
Please use the reply box's picture icon to attach a screenshot.
To find your System Info, please open Lightroom, select Help, select System Information and then copy and paste that info here.
Thank you for responding. Unfortunately I'm now back to not being able to get the installer to run at all. I'm going to uninstall all the stand alone CS programs, run the cleaner, redo disk utility, etc. I'll try to run the installer for lightroom before I reinstall the CS. If there's still an issue, I will let you know.
I solved it by saving my files to an external disk and wiping the hard drive. What a pain in the backside but no more problems.