Photoshop will not open at all. No access to the app.

Thank you for the explanation. I was trying to save space. I will uninstall again then run the CC Cleaner app. Then reinstall on the “default” disk. Your assistance is much appreciated.

“ Moved to new Mac's external ssd.”

Does that mean you’re trying to install the application on an external drive? You can’t do that. It needs to be on an internal drive - preferably on the system drive where it will work most efficiently and fast, but in a pinch it should work on a secondary drive. But not an external.

A large part of the installation will in any case go to the system drive, in your user account, and that part of the installation you cannot move. Then there’s shared files and common files.

At this point you need to run the CC Cleaner app to remove all traces of previous activity, then reinstall fresh.

If you’re running out of disk space, this is not the way to go about it! You only save a couple of GB, which is nothing in the big picture. You can usually free up ten times that space, or more, simply by running a cleanup of your system drive. You can do that from the operating system. In fact, simply emptying the recycle bin will usually free up more space than the Photoshop installation files take up.

As a general rule of thumb, a standard installation of operating system and applications should not take up much more than about 100-120 GB. If it’s much more than that, a cleanup should be considered.