I have been having the same issue. Have you learned what the issue is?
Sorry, I haven't. Quite a number of users seem to have the same problem. I have found it almost impossible to contact anyone at Adobe here in the UK.
I was given the following solution by Adobe Support: (for Mac OS)
Click on "finder" in the doc
Click on the option "go" and in the drop down "go to folder"
Type "~/library" in the pop-up window
Double click on the folder "Application Support" then "Adobe"
Look for folder "OOBE"
Delete this folder by dragging it to trash
Now launch the CC desktop application
You will then have to enter your Adobe id and password and then install Lightroom
The steps are totally unnecessary. Whenever Lightroom team releases a new version, Creative cloud app will not recognize the older version as is not available for download and install for any user anymore. If Lightroom moves from your apps or installed apps section to apps available for install it simply means a new version of Lightroom is available. Once you download and install this version it will automatically update older version to newer version.
Thanks for the help, now that I understand, it makes a little more sense.