Accessing Files on Windows 10 under latest Parallels 11

Hi ,
I have recently upgraded to Windows 10 under Parallels 11 on my partners iMac.
From my Windows 7 (dual boot) machine I can readily access the iMac Windows 10 C drive. However when I do the same from my dual boot Windows 10, I am told
"Partner-IMAC is not accessible. You might not have permission to use this network resource. Contact the administrator of this server to find out if you have access permissions.
Account restrictions are preventing this user from signing in. For example blank passwords aren't allowed, sign-in times a limited, or a policy restriction has been enforced."
Why this difference between Windows 7 and 10?
Any help to solve this is appreciated.

I just noted I can access files on the Partners machine with the device name IMAC-9E498C (this seems to be the Mac partition), but not the Partner-IMAC device which I assume is the Windows partition.

Cheers
Ian