P: Won't start. Ask to change permission of folders, but that doesn't solve.

I'm forwarding to a LR engineer.

Have seen numerous people reporting they have encountered this same problem in our large Improve Photography Facebook page Victoria.  When they pulled the catalog file from backup folder that worked, but Disk Utility and First Aid didn't help.  Didn't go so far as to create a new user is OS X and try that route to fix things, but this looks concerning.

Lightroom brings a dialog box about user permission problem. Pressing on the repair button then brings a second dialog box that says the problem could not be solved automatically and needs to be done manually and points to https://helpx.adobe.com/lightroom/kb/lightroom-cc-2015-4-lightroom-6-4-crashes-on-launch.html
Doing what that page says doesn't solve the problem. Also tried rebooting a.fter

What happens when you try to open Lightroom?