Many users who have upgraded to Lightroom Classic have encountered this error: The catalog named X is too new to be used by this version of Lightroom. Would you like to select a different catalog?
This happens when you accidentally open your Lightroom Classic catalog using Lightroom 6 or CC 2015 and this old version can’t read your newer Lightroom Classic catalog.
To resolve this, choose Quit and then open Lightroom Classic.
Making this mistake is so easy because the program icons are the same for both programs: