Please uninstall both version of Lightroom from the System and restart the machine. Use the below link for Installing Lightroom 6.
Download link: Download Photoshop Lightroom
And before you install the Lightroom 6, you update or install the Adobe Application Manager.
Download the Application Manager
Let us know if that helps.
Thanks a lot. This worked and I installed Applicationmanager and then Lightroom 6.0 that I promptly upgraded to 6.2.
During the LR installation, I was prompted to introduce the license key (which I did), but when I opened LR I found that I was in the CC mode, so I had to go through the procedure of creating a new Adobe account without LR CC membership (as per the link suggested by wobertc below) to be able to re-introduce the license. It seems to work.
Regards, and thanks