Yeah- it showed it as mounted.
I actually managed to fix the problem. The drive had a password protection on it. I actually had to log on to my machine and open and unlock the drive- and then remove the drive password protection.
Then I had the issue of the restore not working because the drive was formatted differently. I eventually found a solution to that problem in a thread somewhere and had to delete the hard drive before doing the restore.
All up- I lost a full day of productivity to be able to return to the point I was at before.
Moral of this story- if you are a user of Photoshop CS6 (and don't want to be trapped into an exploitative adobe subscription to be able to do what you can already do) - DON'T "upgrade" to Catalina!