I'm getting this error message. "The Lightroom catalog named Lightroom 6 Catalog cannot be opened because it is too new to be used by this version of Lightroom. Would you like to select a different catalog?" I know that someone asked for help on this back in April; however, my situation may be different. I have LR5.7 on desktop and laptop. Just uploaded and updated LR6/6.7. After installed it worked fine on desktop, copied it to WD portable backup drive to use on laptop. Put folder in same place a LR5 on backup. Tested on desktop. It opened and all photos there. Connected portable drive to laptop. Went to launch LR6 and receive the error message. I'm clicking LR6 and it's attempting to open LR5. Appreciate your assistance.
What do you mean with 'copied to WD portable backup drive to use on laptop'?
You did install LR6 on the laptop as well, did you?
You need to start the correct app. The LR6 install does not remove LR5. Open explorer/finder and navigate to the LR6 program folder and try to start from there. What is your OS?