I have a MacBook Air running X El Capitan ver. 10.11.5 (15F34).
I purchased Lightroom 6 from Amazon, and got the CD in the mail.
Since my Mac does not have a disc drive, I used my old MacBook Pro to copy the disc onto a USB stick. Plugged it in and ran it from that stick.
I registered it and it proved to be genuine.
Tried installing it and got an Adobe Genuine Software Verification Failure message. Said my product appears to be counterfeit.
Below, I have laid out what I did as per what was suggested in one of the forums
Click on the below link and download Adobe Application Manager and install the same .
Once the installation process is completed, installation box will disappear.
Then open " Applications" folder and locate Adobe Application Manager launch icon and double click on it and update.
It will launch Adobe Creative Cloud app. Quit it . (NOTE: I don't have Creative Cloud, so it was not launched)
Make sure to Force Quit Creative Cloud process from Activity Monitor .
Then try to install Lightroom , it shud work.
After doing all of the above, still ended with same Failure message.