As per title. It's for a standalone machine not connected to the net.
Develop module disabled itself due to non sign in - annoying.
I tried installing LR6 again, but it doesn't even show in the Applications folder, and booting up LR just shows CC.
Please remove all the folder related to Lightroom and trash the installed version as well.
Restart the Machine
Use the below link to download the Lightroom 6 Standalone Version
Once, its installed and working fine. you can update to the latest version.
Let us know if it helps.
For God's sake, don't install that junk 6.2.1!