I had two finder windows open and accidentally changed the name of my old profile (the one I wanted to use), rather than change the 8-character chain in front of the new default profile that was created when I downloaded Thunderbird on the new machine. I even went so far as to throw away what I thought was the new profile and had to drag it back out of the trash. Now the profile I want to use is in the library folder for Thunderbird. It is also in the place where it was created when I first backed up this profile.

When I try to open Thunderbird, I get an error message, "Your Thunderbird profile cannot be loaded. It may be missing or inaccessible." I've tried uninstalling Thunderbird and re-installing, but the same thing happens.