I am using Windows 10 and I believe I am logged in as an administrator. I am the only one that uses this computer, and until recently had no problems with LR. The opening problem started a couple of months ago before I upgraded to the latest version. I figured the upgrade would take care of the problem, but I was wrong.
Using File Explorer (or Windows Explorer if that is what it is called now), go to the folder on your hard drive listed in the error and make sure you have READ and WRITE privileges on that folder and its parent.