Do you have the Photographers Bundle: PS-CC+LR for $10/month, or some other combination of product versions or licenses?
And Adobe licenses are for 2 computers, not three.
Yes, I have the Photographers Bundle.
Owww, I read in a review that it was three. That is actually no problem because I only own 2 PC's.
I think that the problem may be in the OS. I deinstallated the whole CC package and then tried to installate Photoshop back again. The first attempt CC stopped installing after 80% and the second time after 82%. Although CC told me that the installation of Photoshop had failed I could open Photoshop and it looked okay to me. I still think that I have to repair my OS first before I can install CC back again.
If I failed again I will return to you, but I think that after the clean up CC will work again (I hope ).
This is a user-to-user forum and I am just another user like yourself.
After uninstalling all Adobe software, run the CC Cleaner to remove any last remnants.
If LR is asking you to enter a serial number then you may have downloaded and installed the non-CC version of LR which is only licensed with a serial number. If so, then uninstall that, Quit the CC Desktop app, using Gear/Quit or right-click/Quit, then restart CC Desktop, and you should get LR in the App list to install.
There is also a help page for when CC applications are asking for a serial number: