Hello Michael,
     I see that I can add "Parallels Access" but I don't have anything called "Parallels Access Agent" on my Macbook Pro (late 2016) running Mojave.
     How/ where do I find "Parallels Access Agent" ?
     I have Parallels 13 installed, and I get the same error (I've attached a Screen grab):
     Unable to connect Hard Disk 1.
     A file or device required for the operation of Hard Disk 1 does not exist or is used by another process, or you have no permission to access it... etc.
Thanks in advance,
Rajnesh