xcopy cannot find directory path

Greetings all! New here - hope you are all having an exciting summer!

I'm trying to change the default location of my User folder to another drive. I had this same setup function before I upgraded my SSD. Now with a fresh SSD and a fresh install of windows, I'm having trouble copying the User directory to the old drive, where the old user directory still is - ideally I'd like to merge the directories.

I've been following this guide: How To Change User Profile Location in Windows 8 without Registry Hack | Next of Windows

When I try to just create a new user directory

Xcopy asks when I want to create a file or a directory, I press D to proceed and then xcopy says the path specified cannot be found.

Listing the drives with dir shows the paths do exist. Executing the command from either drive changes nothing.

Why would this happen? There aren't any security restrictions as far as I can see. I can create files and folders within the drive in windows, and even install programs to the old programs directory on there as well.

Would it hurt to just click and drag my current profile to the old Users directory, delete the new one and then make the link?

My only solution so far would be to wipe the whole D drive - I would lose a tremendous amount of data (700gb), so I'm determined to find another way.